Merge pull request #2 from Berack96/net-creation

Net creation interactive

.vscode/launch.json

@@ -9,56 +9,49 @@
             "name": "Run1k Simple",
             "request": "launch",
             "mainClass": "net.berack.upo.valpre.Main",
-            "args": "simulation -net example1.net -runs 1000 -p"
+            "args": "simulation -net src/test/resources/example1.net -runs 1000 -p"
         },
         {
             "type": "java",
             "name": "Run1k Complex",
             "request": "launch",
             "mainClass": "net.berack.upo.valpre.Main",
-            "args": "simulation -net example2.net -runs 1000 -p"
-        },
-        {
-            "type": "java",
-            "name": "Run1k Complex EXP",
-            "request": "launch",
-            "mainClass": "net.berack.upo.valpre.Main",
-            "args": "simulation -net example3.net -runs 1000 -p"
+            "args": "simulation -net src/test/resources/example2.net -runs 1000 -p"
         },
         {
             "type": "java",
             "name": "Run Incremental",
             "request": "launch",
             "mainClass": "net.berack.upo.valpre.Main",
-            "args": "simulation -net example3.net -runs 1000 -i \"[Service1:throughput=0.98:0.01],[Service2:utilization=0.98:0.01],[Service2:unavailable=0.98:0.01]\""
+            "args": "simulation -net src/test/resources/example2.net -runs 1000 -i \"[Service1:throughput=0.98:0.01],[Service2:utilization=0.98:0.01],[Service2:unavailable=0.98:0.01]\""
         },
         {
             "type": "java",
             "name": "Run10",
             "request": "launch",
             "mainClass": "net.berack.upo.valpre.Main",
-            "args": "simulation -net example1.net -runs 10 -seed 2007539552"
+            "args": "simulation -net src/test/resources/example1.net -runs 10 -seed 2007539552"
         },
         {
             "type": "java",
             "name": "Plot Simple",
             "request": "launch",
             "mainClass": "net.berack.upo.valpre.Main",
-            "args": "plot -csv example1.csv"
+            "args": "plot -csv src/test/resources/example1.csv"
         },
         {
             "type": "java",
             "name": "Plot Complex",
             "request": "launch",
             "mainClass": "net.berack.upo.valpre.Main",
-            "args": "plot -csv example2.csv"
+            "args": "plot -csv src/test/resources/example2.csv"
         },
         {
             "type": "java",
-            "name": "Build Net",
+            "name": "Interactive Net Builder",
             "request": "launch",
             "mainClass": "net.berack.upo.valpre.Main",
-            "args": "net"
+            "args": "interactive"
         },
     ]
 }

README.md

@@ -5,15 +5,18 @@ Il simulatore è iniziato con il lavoro trovato sul libro di testo [Discrete-Eve
 
 Il risultato è la creazione in una libreria per la simulazione di eventi discreti nella quale si può scegliera la topologia e la quantità di nodi nella rete da simulare.
 
+Questa libreria è stata confrontata con il tool [JMT](https://jmt.sourceforge.net/Download.html) e le reti usate per fare il confronto si possono trovare sotto [le risorse del main](https://github.com/Berack96/upo-valpre/tree/main/src/main/resources).
+
 > [!IMPORTANT]
 > Il JAR risultante che si trova nelle [Releases](https://github.com/Berack96/upo-valpre/releases).\
 > La versione di Java usata è la 23 (precisamente la [23.0.1](https://www.oracle.com/java/technologies/javase/jdk23-archive-downloads.html)).
 
+---
 ### Comandi Jar
 
 Il JAR viene invocato tramite il classico comando java: `java -jar upo-valpre.jar` al quale si aggiungono vari argomenti successivi in base a cosa si vuole fare:
 
-* `java -jar upo-valpre.jar net`\
+* `java -jar upo-valpre.jar interactive`\
 Usato per avviare una sessione interattiva per la creazione di una rete. Da usare se la rete è relativamente breve da descrivere, altrimenti è più comodo usare il codice della libreria per la generazione della rete.\
 Una volta scelta la rete è necessario salvarla in un file per la successiva simulazione e analisi.
 * `java -jar upo-valpre.jar simulation -net <file> [other]`\
@@ -21,33 +24,64 @@ Usato per avviare una simulazione della rete. Nel caso la rete non abbia eventua
 Esistono vari tipi di argomenti per scegliere come fare la simulazione:
   * `-runs <N>` per fare la simulazione N volte
   * `-seed <value>` per dare un seed iniziale scelto
+  * `-i <confidences>` per scegliere gli indici di terminazione delle run di simulazione quando l'intervallo di confidenza associato è raggiunto. Viene ignorato il comando -p se questa opzione è attiva. Il formato da usare è\
+  **\[nodo:statistica=confidenza:errore%\];\[..\]**
   * `-csv <file>` per salvare i risultati delle run in un file csv
   * `-p` per fare le simulazioni in parallelo (ovvero su più thread)
   * `-end <criteria>` per scegliere quando la simulazione finisce nel caso non ci siano dei source limitati nella creazione di arrivi. La tipologia di fine simulazione la si può trovare dentro `EndCriteria` (ovvero MaxArrivals, MaxDepartures, MaxTime) e la formattazione da usare per passare il parametro è la seguente:\
-  **\[Tipo1:param1,..,paramN\];\[..\];\[TipoN:param1,..,paramN\]**
+  **\[tipo:param1,..,paramN\];\[..\]**
 * `java -jar upo-valpre.jar plot -csv <file>`\
 Mostra (con un ambiente grafico) una finestra nella quale si può scegliere quale nodo vedere e ogni statistica associata ad esso. Di seguito un'immagine di esempio:\
 ![1738603552417](image/README/1738603552417.png)
 
-Esistono dei file prefatti per vedere eventuali simulazioni che, nel caso vengano passati come parametri, automaticamente vengono usati:
-* `example1.net`, `example2.net` e `example3.net` per `simulation -net`
-* `example1.csv`, `example2.csv` e `example3.csv` per `plot -csv`
-
+---
 ### Classi Interne
 
-Esistono molteplici classi interne che vengono usate per supportare la simulazione e/o mostrare i risultati. In generale le classi dentro il percorso [net.berack.upo.valpre](https://github.com/Berack96/upo-valpre/tree/main/src/main/java/net/berack/upo/valpre) sono usate per l'utilizzo del jar e quindi non sono essenziali per la simulazione.
+Esistono molteplici classi interne che vengono usate per supportare la simulazione e/o mostrare i risultati. In generale le classi dentro il percorso [net.berack.upo.valpre](src/main/java/net/berack/upo/valpre) sono usate per l'utilizzo del jar e quindi non sono essenziali per la simulazione.
 I percorsi che invece sono direttamente responsabili per la simulazione sono:
-- [net.berack.upo.valpre.rand](https://github.com/Berack96/upo-valpre/tree/main/src/main/java/net/berack/upo/valpre/rand) All'interno del quale si possono trovare:
+- [net.berack.upo.valpre.rand](src/main/java/net/berack/upo/valpre/rand) All'interno del quale si possono trovare:
   - **Rng** che viene usato per il calcolo di numeri pseudo-casuali tramite un seed iniziale e la generazione di molteplici stream di generazione di numeri casuali
   - **Distribution** interfaccia usata per la generazione di un numero casuale di una distribuzione. In questo file esistono molteplici classi interne che implementano l'interfaccia; per esempio: Exponential, Normal, Uniform
-- [net.berack.upo.valpre.sim](https://github.com/Berack96/upo-valpre/tree/main/src/main/java/net/berack/upo/valpre/sim) Package che contiene tutte le parti utili alla simulazione; per esempio la creazione della rete o la simulazione si più thread:
+- [net.berack.upo.valpre.sim](src/main/java/net/berack/upo/valpre/sim) Package che contiene tutte le parti utili alla simulazione; per esempio la creazione della rete o la simulazione si più thread:
   - **Net** che viene usato per rappresentare una rete da simulare.
   - **ServerNode** che viene usato per rappresentare un singolo nodo della rete.
   - **Event** che viene usato per rappresentare un evento della simulazione.
   - **EndCriteria** interfaccia che viene implementata dalle classi interne usata per controllare se e quando la simulazione debba finire.
   - **Simulation** e **SimulationMultiple** che vengono usate per far partire la simulazione; la versione multiple serve ad organizzare molteplici simulazioni su più thread o su un singolo core.
-- [net.berack.upo.valpre.sim.stats](https://github.com/Berack96/upo-valpre/tree/main/src/main/java/net/berack/upo/valpre/sim/stats) Package che contiene tutte le classi utili per la raccolta e l'analisi statistica dei vari valori generati dalla simulazione:
+- [net.berack.upo.valpre.sim.stats](src/main/java/net/berack/upo/valpre/sim/stats) Package che contiene tutte le classi utili per la raccolta e l'analisi statistica dei vari valori generati dalla simulazione:
   - **Result** il risultato di una run e la sua classe interna **Result.Summary** che contiene molteplici risultati di run già analizzati.
   - **NodeStats** contiene indici statistici di un nodo e la sua classe interna **NodeStats.Summary** che contiene molteplici indici statistici già analizzati.
   - **ConsoleTable** utile per mostrare i risultati in console sottoforma di tabella
   - **CsvResult** utile per la lettura/scrittura dei risultati in formato csv
+
+---
+### Esempi
+
+Nel jar sono presenti già 2 reti per fare degli esperimenti e/o testare se il tool funziona correttamente. Per poter vedere una run usando questi esempi basta far partire il tool in modalità interattiva e scegliere di caricare gli esempi.\
+`java -jar upo-valpre.jar interactive`
+
+##### Primo esempio
+![1741862746304](image/README/1741862746304.png)\
+Il primo è `example1`; è una rete composta da una fonte di clienti (Source) che arrivano con tasso esponenziale (λ=0.222 e quindi media 4.5) e un centro di servizio (Queue) con tasso di servizio distribuito come una normale (μ=3.2, σ=0.6).\
+Se si effettua una simulazione si vedranno i risultati sulla console in questo modo:
+![1741860064265](image/README/1741860064265.png)
+
+Il tool JMT con la stessa rete produce i seguenti risultati che sono molto simili a quelli prodotti dalla libreria:\
+Queue Response Time = 7.3022 con un range [7.1456, 7.4589]\
+Queue Throughput = 0.2226 con un range [0.2182, 0.2271]\
+Queue Utilization = 0.7111 con un range [0.6959, 0.7262]
+
+##### Secondo esempio
+![1741863043733](image/README/1741863043733.png)\
+Il secondo esempio è `example2`; è una rete composta da una fonte di clienti (Source) che arrivano con tasso esponenziale (λ=1.5 e quindi media 0.666), un centro di servizio (Service1) con tasso di servizio distribuito come una esponenziale (λ=2.0 e quindi media 0.5) e un altro centro di servizio (Service2) con tasso di servizio distribuito come una esponenziale (λ=3.5 e quindi media 0.2857) e con un tempo di indisponibilità che viene attivato con probabilità 10% e distribuito con una eseponenziale (λ=10.0 e quindi media 0.1)\
+Se si effettua una simulazione si vedranno i risultati sulla console in questo modo:
+![1741862486547](image/README/1741862486547.png)
+
+Il tool JMT con la stessa rete produce i seguenti risultati che sono molto simili a quelli prodotti dalla libreria:\
+Service1 Response Time ~ 1.9866\
+Busy2 Response Time ~ 0.2825\
+Queue2 Response Time ~ 0.2279\
+Service1 Utilization ~ 0.7488\
+Calibration Number of Customers ~ 0.0150\
+Busy2 Number of Customers ~ 0.4279\
+Throughput ~ 1.5000

pom.xml

@@ -13,30 +13,6 @@
         <maven.compiler.target>23</maven.compiler.target>
     </properties>
 
-    <build>
-        <plugins>
-            <!-- Compilazione Java con Maven -->
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-compiler-plugin</artifactId>
-                <version>3.8.1</version>
-                <configuration>
-                    <source>23</source>
-                    <target>23</target>
-                </configuration>
-            </plugin>
-            <!-- Maven plugin per eseguire l'applicazione JavaFX -->
-            <plugin>
-                <groupId>org.openjfx</groupId>
-                <artifactId>javafx-maven-plugin</artifactId>
-                <version>0.0.8</version>
-                <configuration>
-                    <mainClass>net.berack.upo.valpre.Main</mainClass>
-                </configuration>
-            </plugin>
-        </plugins>
-    </build>
-
     <dependencies>
         <dependency>
             <groupId>org.junit.jupiter</groupId>

src/main/java/net/berack/upo/valpre/InteractiveConsole.java

@@ -0,0 +1,267 @@
+package net.berack.upo.valpre;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.PrintStream;
+import java.util.Scanner;
+import java.util.concurrent.ExecutionException;
+import java.util.function.Function;
+
+import com.esotericsoftware.kryo.KryoException;
+
+import net.berack.upo.valpre.rand.Distribution;
+import net.berack.upo.valpre.sim.Net;
+import net.berack.upo.valpre.sim.ServerNode;
+
+/**
+ * Interactive net builder. This class allows the user to build a net by adding
+ * nodes and connections. The user can also save the net to a file.
+ */
+public class InteractiveConsole {
+
+    private Net net = new Net();
+    private final PrintStream out;
+    private final Scanner scanner;
+
+    /**
+     * Create a new interactive net builder. Uses System.in and System.out.
+     */
+    public InteractiveConsole() {
+        this(System.out, System.in);
+    }
+
+    /**
+     * Create a new interactive net builder.
+     * 
+     * @param out the output stream
+     * @param in  the input stream
+     */
+    public InteractiveConsole(PrintStream out, InputStream in) {
+        this.out = out;
+        this.scanner = new Scanner(in);
+    }
+
+    /**
+     * Run the interactive net builder.
+     */
+    public Net run() {
+        while (true) {
+            try {
+                var choice = choose(this.net + "\nChoose the next step to do:",
+                        "Add a node", "Add a connection", "Save the net", "Load net", "Clear", "Run", "Exit");
+                switch (choice) {
+                    case 1 -> this.buildNode();
+                    case 2 -> this.buildConnection();
+                    case 3 -> this.net.save(ask("Enter the filename: "));
+                    case 4 -> this.loadNet();
+                    case 5 -> this.net = new Net();
+                    case 6 -> this.simpleRuns();
+                    default -> {
+                        this.scanner.close();
+                        return this.net;
+                    }
+                }
+            } catch (Exception e) {
+                e.printStackTrace();
+            }
+        }
+    }
+
+    /**
+     * Build a node as a source, terminal, queue, or queue with unavailable time.
+     */
+    private void buildNode() {
+        var choice = choose("Choose the type of node to create:", "Source", "Terminal", "Queue",
+                "Queue with unavailable time");
+        var name = ask("Node name: ");
+        var distribution = askDistribution("Service distribution");
+
+        var node = switch (choice) {
+            case 1 -> ServerNode.Builder.source(name, distribution);
+            case 2 -> {
+                var limit = ask("Arrivals limit (0 for Int.Max): ", Integer::parseInt);
+                if (limit <= 0)
+                    limit = Integer.MAX_VALUE;
+                yield ServerNode.Builder.terminal(name, limit, distribution);
+            }
+            case 3 -> {
+                var servers = ask("Number of servers: ", Integer::parseInt);
+                yield ServerNode.Builder.queue(name, servers, distribution, null);
+            }
+            case 4 -> {
+                var servers = ask("Number of servers: ", Integer::parseInt);
+                var unavailable = askDistribution("Unavailable distribution");
+                yield ServerNode.Builder.queue(name, servers, distribution, unavailable);
+            }
+            default -> null;
+        };
+
+        if (node != null)
+            this.net.addNode(node);
+    }
+
+    /**
+     * Build a connection.
+     */
+    private void buildConnection() {
+        var source = ask("Enter the source node: ");
+        var target = ask("Enter the target node: ");
+        var weight = ask("Enter the weight: ", Double::parseDouble);
+        var sourceNode = this.net.getNode(source);
+        var targetNode = this.net.getNode(target);
+        this.net.addConnection(sourceNode, targetNode, weight);
+    }
+
+    /**
+     * Load a net from a file or from examples.
+     */
+    private void loadNet() throws KryoException, IOException {
+        var choice = choose("Choose the type of net to load:", "From file", "From examples");
+        this.net = switch (choice) {
+            case 1 -> Net.load(ask("Enter the filename: "));
+            case 2 -> {
+                var choice2 = choose("Choose the example to load:",
+                        "Example 1: Source -> Queue",
+                        "Example 2: Source -> Queue -> Queue");
+                yield switch (choice2) {
+                    case 1 -> NetExamples.getNet1();
+                    case 2 -> NetExamples.getNet2();
+                    default -> null;
+                };
+            }
+            default -> null;
+        };
+    }
+
+    /**
+     * Run the simulation with the net.
+     */
+    private void simpleRuns() throws InterruptedException, ExecutionException, IOException {
+        var choice = choose("Choose what to do:", "100 Run", "1K Runs", "1K Runs + Plot");
+        switch (choice) {
+            case 1 -> new SimulationBuilder(net).setMaxRuns(100).setParallel(true).run();
+            case 2 -> new SimulationBuilder(net).setMaxRuns(1000).setParallel(true).run();
+            case 3 -> {
+                var randName = "rand" + System.currentTimeMillis() + ".csv";
+                new SimulationBuilder(net).setMaxRuns(1000).setParallel(true).setCsv(randName).run();
+                new Plot(randName).show();
+                new File(randName).delete();
+            }
+            default -> {
+            }
+        }
+    }
+
+    /**
+     * Ask the user for a distribution.
+     * 
+     * @return the distribution
+     */
+    private Distribution askDistribution(String ask) {
+        var choice = choose(ask + ":", "Exponential", "Uniform", "Erlang",
+                "UnavailableTime", "Normal", "NormalBoxMuller", "None");
+
+        return switch (choice) {
+            case 1 -> {
+                var lambda = ask("Lambda: ", Double::parseDouble);
+                yield new Distribution.Exponential(lambda);
+            }
+            case 2 -> {
+                var min = ask("Min: ", Double::parseDouble);
+                var max = ask("Max: ", Double::parseDouble);
+                yield new Distribution.Uniform(min, max);
+            }
+            case 3 -> {
+                var k = ask("K: ", Integer::parseInt);
+                var lambda = ask("Lambda: ", Double::parseDouble);
+                yield new Distribution.Erlang(k, lambda);
+            }
+            case 4 -> {
+                var probability = ask("Probability: ", Double::parseDouble);
+                var unavailable = askDistribution("Unavailable distribution");
+                yield new Distribution.UnavailableTime(probability, unavailable);
+            }
+            case 5 -> {
+                var mean = ask("Mean: ", Double::parseDouble);
+                var stdDev = ask("Standard deviation: ", Double::parseDouble);
+                yield new Distribution.Normal(mean, stdDev);
+            }
+            case 6 -> {
+                var mean = ask("Mean: ", Double::parseDouble);
+                var stdDev = ask("Standard deviation: ", Double::parseDouble);
+                yield new Distribution.NormalBoxMuller(mean, stdDev);
+            }
+            default -> null;
+        };
+    }
+
+    /**
+     * Ask the user a question.
+     * 
+     * @param ask the question to ask
+     * @return the answer
+     */
+    private String ask(String ask) {
+        return ask(ask, Function.identity());
+    }
+
+    /**
+     * Ask the user a question.
+     * 
+     * @param ask          the question to ask
+     * @param parser       the parser to use
+     * @param defaultValue the default value
+     * @return the answer
+     */
+    private <T> T ask(String ask, Function<String, T> parser) {
+        var totalRows = ask.chars().filter(ch -> ch == '\n').count();
+
+        var ask2 = "\033[" + totalRows + "A" + ask;
+        var first = true;
+
+        try {
+            while (true) {
+                this.out.print(first ? ask : ask2);
+                var line = this.scanner.nextLine();
+                first = false;
+
+                try {
+                    var value = parser.apply(line);
+                    return value;
+                } catch (Exception e) {
+                    this.out.print("\033[A\033[K"); // clear the line
+                }
+            }
+        } catch (Exception e) {
+            return null; // normally when the scanner is closed
+        }
+    }
+
+    /**
+     * Ask the user to choose an option.
+     * 
+     * @param ask     the question to ask
+     * @param options the options to choose from
+     * @return the choice
+     */
+    private int choose(String ask, String... options) {
+        var builder = new StringBuilder();
+        builder.append(ask).append("\n");
+        for (int i = 0; i < options.length; i++) {
+            builder.append(i + 1).append(". ").append(options[i]).append("\n");
+        }
+        builder.append("> ");
+
+        var string = builder.toString();
+        var choice = 0;
+        choice = ask(string, val -> {
+            var x = Integer.parseInt(val);
+            if (x < 1 || x > options.length)
+                throw new NumberFormatException(); // retry the question
+            return x;
+        });
+
+        return choice;
+    }
+}

src/main/java/net/berack/upo/valpre/Main.java

@@ -31,10 +31,7 @@ public class Main {
                     var plot = new Plot(csv);
                     plot.show();
                 }
-                case "net" -> {
-                    var net = new NetBuilderInteractive();
-                    net.run();
-                }
+                case "interactive" -> new InteractiveConsole().run();
                 default -> exit("Invalid program!");
             }
         } catch (Exception e) {
@@ -86,11 +83,11 @@ public class Main {
             var uri = Main.class.getProtectionDomain().getCodeSource().getLocation().toURI();
             var name = new File(uri).getName();
             System.err.println(message);
-            System.out.println("Usage: java -jar " + name + ".jar [simulation|plot|net] [args]");
+            System.out.println("Usage: java -jar " + name + ".jar [simulation|plot|interactive] [args]");
             System.out.println("simulation args: -net <net> [-csv <csv>] [-runs <runs>] [-seed <seed>]"
                     + "[-p] [-end <end>] [-i <indices>]");
             System.out.println("plot args: -csv <csv>");
-            System.out.println("net args: none");
+            System.out.println("interactive: no args needed");
             System.exit(1);
         } catch (URISyntaxException e) {
             e.printStackTrace();

src/main/java/net/berack/upo/valpre/NetBuilderInteractive.java

@@ -1,186 +0,0 @@
-package net.berack.upo.valpre;
-
-import java.util.function.Function;
-import net.berack.upo.valpre.rand.Distribution;
-import net.berack.upo.valpre.sim.Net;
-import net.berack.upo.valpre.sim.ServerNode;
-
-public class NetBuilderInteractive {
-
-    private final Net net = new Net();
-
-    /**
-     * Run the interactive net builder.
-     * 
-     * @param args the arguments
-     */
-    public void run() {
-        while (true) {
-            try {
-                var choice = choose("Choose the next step to do:",
-                        "Add a node", "Add a connection", "Print Nodes", "Save the net", "Exit");
-                switch (choice) {
-                    case 1 -> {
-                        var node = this.buildNode();
-                        this.net.addNode(node);
-                    }
-                    case 2 -> {
-                        var source = ask("Enter the source node: ");
-                        var target = ask("Enter the target node: ");
-                        var weight = ask("Enter the weight: ", Double::parseDouble, 0.0);
-                        var sourceNode = this.net.getNode(source);
-                        var targetNode = this.net.getNode(target);
-                        this.net.addConnection(sourceNode, targetNode, weight);
-                    }
-                    case 3 -> this.printNodes();
-                    case 4 -> this.net.save(ask("Enter the filename: "));
-                    case 5 -> System.exit(0);
-                }
-            } catch (Exception e) {
-                e.printStackTrace();
-            }
-        }
-    }
-
-    /**
-     * Print the nodes in the net.
-     */
-    private void printNodes() {
-        var builder = new StringBuilder();
-        builder.append("Nodes:\n");
-        for (var i = 0; i < this.net.size(); i++) {
-            var name = this.net.getNode(i).name;
-            builder.append(name).append(" -> ");
-
-            for (var connection : this.net.getChildren(i)) {
-                var child = this.net.getNode(connection.index);
-                builder.append(child.name).append("(").append(connection.weight).append("), ");
-            }
-
-            builder.delete(builder.length() - 2, builder.length());
-            builder.append("\n");
-        }
-        System.out.print(builder.toString());
-    }
-
-    /**
-     * Build a node.
-     * 
-     * @return the node
-     */
-    private ServerNode buildNode() {
-        var choice = choose("Choose the type of node to create:", "Source", "Queue");
-        var name = ask("Node name: ");
-        var distribution = askDistribution("Service distribution");
-
-        return switch (choice) {
-            case 1 -> {
-                var limit = ask("Arrivals limit (0 for Int.Max): ", Integer::parseInt, 1);
-                if (limit <= 0)
-                    limit = Integer.MAX_VALUE;
-                yield ServerNode.Builder.sourceLimited(name, limit, distribution);
-            }
-            case 2 -> {
-                var servers = ask("Number of servers: ", Integer::parseInt, 1);
-                var unavailable = askDistribution("Unavailable distribution");
-                yield ServerNode.Builder.queue(name, servers, distribution, unavailable);
-            }
-            default -> null;
-        };
-    }
-
-    /**
-     * Ask the user for a distribution.
-     * 
-     * @return the distribution
-     */
-    public static Distribution askDistribution(String ask) {
-        var choice = choose(ask + ":", "Exponential", "Uniform", "Erlang",
-                "UnavailableTime", "Normal", "NormalBoxMuller", "None");
-
-        return switch (choice) {
-            case 1 -> {
-                var lambda = ask("Lambda: ", Double::parseDouble, 1.0);
-                yield new Distribution.Exponential(lambda);
-            }
-            case 2 -> {
-                var min = ask("Min: ", Double::parseDouble, 0.0);
-                var max = ask("Max: ", Double::parseDouble, 1.0);
-                yield new Distribution.Uniform(min, max);
-            }
-            case 3 -> {
-                var k = ask("K: ", Integer::parseInt, 1);
-                var lambda = ask("Lambda: ", Double::parseDouble, 1.0);
-                yield new Distribution.Erlang(k, lambda);
-            }
-            case 4 -> {
-                var probability = ask("Probability: ", Double::parseDouble, 0.0);
-                var unavailable = askDistribution("Unavailable distribution");
-                yield new Distribution.UnavailableTime(probability, unavailable);
-            }
-            case 5 -> {
-                var mean = ask("Mean: ", Double::parseDouble, 0.0);
-                var stdDev = ask("Standard deviation: ", Double::parseDouble, 1.0);
-                yield new Distribution.Normal(mean, stdDev);
-            }
-            case 6 -> {
-                var mean = ask("Mean: ", Double::parseDouble, 0.0);
-                var stdDev = ask("Standard deviation: ", Double::parseDouble, 1.0);
-                yield new Distribution.NormalBoxMuller(mean, stdDev);
-            }
-            default -> null;
-        };
-    }
-
-    /**
-     * Ask the user a question.
-     * 
-     * @param ask the question to ask
-     * @return the answer
-     */
-    private static String ask(String ask) {
-        return ask(ask, Function.identity(), "");
-    }
-
-    /**
-     * Ask the user a question.
-     * 
-     * @param ask          the question to ask
-     * @param parser       the parser to use
-     * @param defaultValue the default value
-     * @return the answer
-     */
-    private static <T> T ask(String ask, Function<String, T> parser, T defaultValue) {
-        System.out.print(ask);
-        try {
-            var line = System.console().readLine();
-            return parser.apply(line);
-        } catch (Exception e) {
-            System.out.println("Invalid input: " + e.getMessage());
-            return defaultValue;
-        }
-    }
-
-    /**
-     * Ask the user to choose an option.
-     * 
-     * @param ask     the question to ask
-     * @param options the options to choose from
-     * @return the choice
-     */
-    private static int choose(String ask, String... options) {
-        var builder = new StringBuilder();
-        builder.append(ask).append("\n");
-        for (int i = 0; i < options.length; i++) {
-            builder.append(i + 1).append(". ").append(options[i]).append("\n");
-        }
-        builder.append("> ");
-
-        var string = builder.toString();
-        var choice = 0;
-        while (choice < 1 || choice > options.length)
-            choice = ask(string, Integer::parseInt, 0);
-
-        return choice;
-    }
-}

src/main/java/net/berack/upo/valpre/NetExamples.java

@@ -0,0 +1,94 @@
+package net.berack.upo.valpre;
+
+import net.berack.upo.valpre.rand.Distribution;
+import net.berack.upo.valpre.sim.Net;
+import net.berack.upo.valpre.sim.ServerNode;
+
+/**
+ * This class provides two example networks.
+ * The first network is composed of a terminal node and a queue node.
+ * The second network is composed of a terminal node and two queue nodes.
+ */
+public final class NetExamples {
+    /**
+     * Return the first example network.
+     * The net is composed of a terminal node and a queue node.
+     * The terminal node generates 10000 jobs with an exponential distribution 4.5.
+     * The queue node has a capacity of 1 and a service time of 3.2 with a standard
+     * deviation of 0.6.
+     * The terminal node is connected to the queue node with a probability of 1.0.
+     * 
+     * @return the first example network
+     */
+    public static Net getNet1() {
+        var exp0_22 = new Distribution.Exponential(1.0 / 4.5);
+        var norm3_2 = new Distribution.NormalBoxMuller(3.2, 0.6);
+        var spawn = 10000;
+        return getNet1(spawn, exp0_22, norm3_2);
+    }
+
+    /**
+     * Return the first example network.
+     * The net is composed of a terminal node and a queue node.
+     * The terminal node is connected to the queue node.
+     * 
+     * @param spawn  the number of jobs to generate
+     * @param source the distribution of the source node
+     * @param queue  the distribution of the queue node
+     * @return the first example network
+     */
+    public static Net getNet1(int spawn, Distribution source, Distribution queue) {
+        var net1 = new Net();
+        net1.addNode(ServerNode.Builder.terminal("Source", spawn, source));
+        net1.addNode(ServerNode.Builder.queue("Queue", 1, queue));
+        net1.addConnection(0, 1, 1.0);
+        return net1;
+    }
+
+    /**
+     * Return the second example network.
+     * The net is composed of a terminal node and two queue nodes.
+     * The terminal node generates 10000 jobs with an exponential distribution 1.5.
+     * The first queue node has a capacity of 1 and a service time of 2.0.
+     * The second queue node has a capacity of 1 and a service time of 3.5.
+     * The second queue node has an unavailable time of 0.1 with an exponential
+     * distribution of 10.0.
+     * The terminal node is connected to the first queue node.
+     * The first queue node is connected to the second queue node.
+     * 
+     * @return the second example network
+     */
+    public static Net getNet2() {
+        var exp1_5 = new Distribution.Exponential(1.5);
+        var exp2 = new Distribution.Exponential(2.0);
+        var exp3_5 = new Distribution.Exponential(3.5);
+        var exp10 = new Distribution.Exponential(10.0);
+        var unExp = new Distribution.UnavailableTime(0.1, exp10);
+        var spawn = 10000;
+        return getNet2(spawn, exp1_5, exp2, exp3_5, unExp);
+    }
+
+    /**
+     * Return the second example network.
+     * The net is composed of a terminal node and two queue nodes.
+     * The terminal node is connected to the first queue node.
+     * The first queue node is connected to the second queue node.
+     * 
+     * @param spawn    the number of jobs to generate
+     * @param source   the distribution of the source node
+     * @param service1 the distribution of the first queue node
+     * @param service2 the distribution of the second queue node
+     * @param unExp    the distribution of the unavailable time
+     * @return the second example network
+     */
+    public static Net getNet2(int spawn, Distribution source, Distribution service1, Distribution service2,
+            Distribution unExp) {
+        var net3 = new Net();
+        net3.addNode(ServerNode.Builder.terminal("Source", spawn, source));
+        net3.addNode(ServerNode.Builder.queue("Service1", 1, service1));
+        net3.addNode(ServerNode.Builder.queue("Service2", 1, service2, unExp));
+        net3.addConnection(0, 1, 1.0);
+        net3.addConnection(1, 2, 1.0);
+        return net3;
+    }
+}

src/main/java/net/berack/upo/valpre/Parameters.java

@@ -1,8 +1,5 @@
 package net.berack.upo.valpre;
 
-import java.io.FileInputStream;
-import java.io.FileNotFoundException;
-import java.io.InputStream;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.function.Function;
@@ -194,23 +191,4 @@ public class Parameters {
             throw new IllegalArgumentException("Invalid arguments");
         }
     }
-
-    /**
-     * Get the file or the example file if it is present.
-     * 
-     * @param file the file to get
-     * @return the file or the example file
-     * @throws FileNotFoundException if the file is not found
-     */
-    public static InputStream getFileOrExample(String file) throws FileNotFoundException {
-        if (file == null)
-            return null;
-
-        if (file.startsWith("example")) {
-            var resource = Parameters.class.getClassLoader().getResourceAsStream(file);
-            if (resource != null)
-                return resource;
-        }
-        return new FileInputStream(file);
-    }
 }

src/main/java/net/berack/upo/valpre/Plot.java

@@ -41,12 +41,7 @@ public class Plot {
      * @throws IOException if anything happens while reading the file
      */
     public Plot(String csv) throws IOException {
-        var stream = Parameters.getFileOrExample(csv);
-        if (stream == null)
-            throw new IllegalArgumentException("CSV file needed!");
-        var results = CsvResult.loadResults(stream);
-        stream.close();
-
+        var results = new CsvResult(csv).loadResults();
         this.summary = new Result.Summary(results);
 
         var nodes = this.summary.getNodes().toArray(new String[0]);

src/main/java/net/berack/upo/valpre/SimulationBuilder.java

@@ -2,6 +2,7 @@ package net.berack.upo.valpre;
 
 import java.io.FileNotFoundException;
 import java.io.IOException;
+import java.io.PrintStream;
 import java.util.concurrent.ExecutionException;
 import com.esotericsoftware.kryo.KryoException;
 
@@ -13,6 +14,7 @@ import net.berack.upo.valpre.sim.EndCriteria.MaxTime;
 import net.berack.upo.valpre.sim.Net;
 import net.berack.upo.valpre.sim.SimulationMultiple;
 import net.berack.upo.valpre.sim.stats.CsvResult;
+import net.berack.upo.valpre.sim.stats.Result;
 
 /**
  * This class is responsible for running the simulation. It parses the arguments
@@ -35,10 +37,8 @@ public class SimulationBuilder {
      */
     public SimulationBuilder(String netFile) throws IOException {
         try {
-            var file = Parameters.getFileOrExample(netFile);
-            this.net = Net.load(file);
+            this.net = Net.load(netFile);
             this.confidences = new ConfidenceIndices(this.net);
-            file.close();
         } catch (FileNotFoundException e) {
             throw new IllegalArgumentException("Net file needed!");
         } catch (KryoException e) {
@@ -230,23 +230,38 @@ public class SimulationBuilder {
      * @throws ExecutionException   If the simulation has an error.
      * @throws IOException          If the CSV file has a problem.
      */
-    public void run() throws InterruptedException, ExecutionException, IOException {
+    public Result.Summary run() throws InterruptedException, ExecutionException, IOException {
+        return this.run(System.out);
+    }
+
+    /**
+     * Run the simulation with the given parameters.
+     * At the end it prints the results and saves them to a CSV file if requested.
+     * 
+     * @param out the output stream to print the results
+     * @throws InterruptedException If the simulation is interrupted.
+     * @throws ExecutionException   If the simulation has an error.
+     * @throws IOException          If the CSV file has a problem.
+     */
+    public Result.Summary run(PrintStream out) throws InterruptedException, ExecutionException, IOException {
         var nano = System.nanoTime();
         var sim = new SimulationMultiple(this.net);
         var summary = switch (this.type) {
-            case Incremental -> sim.runIncremental(this.seed, this.runs, this.confidences, this.endCriteria);
+            case Incremental -> sim.runIncremental(this.seed, this.runs, out, this.confidences, this.endCriteria);
             case Parallel -> sim.runParallel(this.seed, this.runs, this.endCriteria);
             case Normal -> sim.run(this.seed, this.runs, this.endCriteria);
         };
         nano = System.nanoTime() - nano;
 
-        System.out.print(summary);
-        System.out.println("Final time " + nano / 1e6 + "ms");
+        out.print(summary);
+        out.println("Final time " + nano / 1e6 + "ms");
 
         if (csv != null) {
             new CsvResult(this.csv).saveResults(summary.getRuns());
-            System.out.println("Data saved to " + this.csv);
+            out.println("Data saved to " + this.csv);
         }
+
+        return summary;
     }
 
     /**

src/main/java/net/berack/upo/valpre/rand/Distribution.java

@@ -32,6 +32,36 @@ public interface Distribution {
         return sample;
     }
 
+    /**
+     * Returns a string representation of the distribution.
+     * In case the distribution is null, an empty string is returned.
+     * 
+     * @param distribution The distribution to represent.
+     * @return A string representation of the distribution.
+     * @throws IllegalArgumentException if the field cannot be accessed
+     * @throws IllegalAccessException   if the field cannot be accessed
+     */
+    public static String toString(Distribution distribution) throws IllegalArgumentException, IllegalAccessException {
+        if (distribution == null)
+            return "";
+
+        var builder = new StringBuilder();
+        var dist = distribution.getClass();
+
+        builder.append(dist.getSimpleName()).append('(');
+        for (var param : dist.getFields()) {
+            var paramValue = param.get(distribution);
+            var str = paramValue instanceof Distribution
+                    ? toString((Distribution) paramValue)
+                    : paramValue;
+
+            builder.append(str).append(", ");
+        }
+
+        builder.delete(builder.length() - 2, builder.length()).append(')');
+        return builder.toString();
+    }
+
     /**
      * Represents an exponential distribution.
      */

src/main/java/net/berack/upo/valpre/sim/Event.java

@@ -23,11 +23,7 @@ public class Event implements Comparable<Event> {
 
     @Override
     public int compareTo(Event other) {
-        if (this.time < other.time)
-            return -1;
-        if (this.time == other.time)
-            return 0;
-        return 1;
+        return Double.compare(this.time, other.time);
     }
 
     /**

src/main/java/net/berack/upo/valpre/sim/Net.java

@@ -75,7 +75,6 @@ public final class Net implements Iterable<ServerNode> {
      * @param weight The probability of the child node.
      * @throws IndexOutOfBoundsException if one of the two nodes are not in the net
      * @throws IllegalArgumentException  if the weight is negative or zero
-     * @throws IllegalArgumentException  if the child is a source node
      */
     public void addConnection(int parent, int child, double weight) {
         if (weight <= 0)
@@ -85,9 +84,6 @@ public final class Net implements Iterable<ServerNode> {
         if (parent < 0 || child < 0 || parent > max || child > max)
             throw new IndexOutOfBoundsException("One of the nodes does not exist");
 
-        if (this.servers.get(child).spawnArrivals > 0)
-            throw new IllegalArgumentException("Can't connect to a source node");
-
         var list = this.connections.get(parent);
         list.removeIf(conn -> conn.index == child);
         list.add(new Connection(child, weight));
@@ -170,14 +166,13 @@ public final class Net implements Iterable<ServerNode> {
             for (var conn : list)
                 sum += conn.weight;
 
-            var newOne = new Connection[list.size()];
-            for (var i = 0; i < list.size(); i++) {
-                var conn = list.get(i);
+            var newOne = new ArrayList<Connection>();
+            for (var conn : list) {
                 var newWeight = conn.weight / sum;
-                newOne[i] = new Connection(conn.index, newWeight);
+                newOne.add(new Connection(conn.index, newWeight));
             }
 
-            this.connections.set(node, List.of(newOne));
+            this.connections.set(node, newOne);
         }
     }
 
@@ -249,6 +244,56 @@ public final class Net implements Iterable<ServerNode> {
         }
     }
 
+    /**
+     * Create a copy of the net passed as input.
+     * The new net will have the same nodes and connections.
+     * 
+     * @param net the net to copy
+     * @return a new Net object
+     */
+    public static Net copyOf(Net net) {
+        var newNet = new Net();
+
+        for (var index = 0; index < net.size(); index++) {
+            var node = net.servers.get(index);
+            var conn = net.connections.get(index);
+            conn = new ArrayList<>(conn);
+
+            newNet.indices.put(node, index);
+            newNet.servers.add(node);
+            newNet.connections.add(conn);
+        }
+
+        return newNet;
+    }
+
+    @Override
+    public String toString() {
+        var builder = new StringBuilder();
+        try {
+            for (var node : this.servers) {
+                builder.append(node)
+                        .append(" -> ");
+
+                for (var child : this.getChildren(this.indices.get(node))) {
+                    var childNode = this.servers.get(child.index);
+                    builder.append(childNode.name)
+                            .append("(")
+                            .append(child.weight)
+                            .append("), ");
+                }
+
+                builder.delete(builder.length() - 2, builder.length())
+                        .append("\n");
+            }
+
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+
+        return builder.toString();
+    }
+
     /**
      * A Static inner class used to represent the connection of a node
      */

src/main/java/net/berack/upo/valpre/sim/ServerNode.java

@@ -18,7 +18,7 @@ public class ServerNode {
     /**
      * Creates a generic node with the given name and distribution.
      * The servers number must be 1 or higher; if lower will be put to 1.
-     * The spawn number must be 0 or higher; if lower will be put to 0.
+     * The spawn number must be 0 or higher; if lower will be put to -1 (infinite).
      * The queue number must be equal or higher than the servers number; if lower
      * will be put to the servers number.
      * The service distribution can't be null, otherwise an exception is thrown.
@@ -37,7 +37,7 @@ public class ServerNode {
         if (servers <= 0)
             servers = 1;
         if (spawn < 0)
-            spawn = 0;
+            spawn = -1;
         if (queue < servers)
             queue = servers;
 
@@ -71,6 +71,28 @@ public class ServerNode {
         return Distribution.getPositiveSample(this.unavailable, rng);
     }
 
+    @Override
+    public String toString() {
+        try {
+            var build = new StringBuilder()
+                    .append(this.name)
+                    .append("[servers:")
+                    .append(this.maxServers)
+                    .append(", queue:")
+                    .append(this.maxQueue)
+                    .append(", spawn:")
+                    .append(this.spawnArrivals)
+                    .append(", ")
+                    .append(Distribution.toString(this.service));
+            if (this.unavailable != null)
+                build.append(", u:").append(Distribution.toString(this.unavailable));
+            return build.append(']').toString();
+        } catch (Exception e) {
+            e.printStackTrace();
+            return "";
+        }
+    }
+
     @Override
     public boolean equals(Object obj) {
         if (!(obj instanceof ServerNode))
@@ -183,26 +205,27 @@ public class ServerNode {
 
         /**
          * Creates a source node with the given name and distribution.
-         * It swpawns infinite arrivals (Integer.MAX_VALUE).
+         * It swpawns infinite arrivals (-1).
          * 
          * @param name         The name of the node.
          * @param distribution The distribution of the inter-arrival times.
          * @return The created source node.
          */
         public static ServerNode source(String name, Distribution distribution) {
-            return new Builder(name, distribution).spawn(Integer.MAX_VALUE).build();
+            return new Builder(name, distribution).spawn(-1).build();
         }
 
         /**
-         * Creates a source node with the given name, distribution, and number of
+         * Creates a terminal node with the given name, distribution, and number of
          * arrivals to spawn.
+         * Once it has finished spawning the arrivals, it will not spawn anymore.
          * 
          * @param name          The name of the node.
          * @param service       The distribution of the inter-arrival times.
          * @param spawnArrivals The number of arrivals to spawn.
          * @return The created source node.
          */
-        public static ServerNode sourceLimited(String name, int spawnArrivals, Distribution service) {
+        public static ServerNode terminal(String name, int spawnArrivals, Distribution service) {
             return new Builder(name, service).spawn(spawnArrivals).build();
         }
 

src/main/java/net/berack/upo/valpre/sim/ServerNodeState.java

@@ -69,7 +69,7 @@ public class ServerNodeState {
      * @return True if the node should spawn an arrival, false otherwise.
      */
     public boolean shouldSpawnArrival() {
-        return this.node.spawnArrivals > this.stats.numArrivals;
+        return this.node.spawnArrivals < 0 || this.node.spawnArrivals > this.stats.numArrivals;
     }
 
     /**
@@ -158,6 +158,23 @@ public class ServerNodeState {
         return null;
     }
 
+    /**
+     * Get a random child based on the weights of the children and the random number
+     * generator passed as input
+     * 
+     * @param rng the random number generator
+     * @return the index of the child or -1 if no child is selected
+     */
+    public int getRandomChild(Rng rng) {
+        var random = rng.random();
+        for (var child : this.children) {
+            random -= child.weight;
+            if (random <= 0)
+                return child.index;
+        }
+        return -1;
+    }
+
     /**
      * Create an arrival event to a child node based on the node and the time passed
      * as input
@@ -168,12 +185,7 @@ public class ServerNodeState {
      *         otherwise
      */
     public Event spawnArrivalToChild(double time, Rng rng) {
-        var random = rng.random();
-        for (var child : this.children) {
-            random -= child.weight;
-            if (random <= 0)
-                return Event.newArrival(child.index, time);
-        }
-        return null;
+        var child = this.getRandomChild(rng);
+        return child > -1 ? Event.newArrival(child, time) : null;
     }
 }

src/main/java/net/berack/upo/valpre/sim/Simulation.java

@@ -1,6 +1,5 @@
 package net.berack.upo.valpre.sim;
 
-import java.util.ArrayList;
 import java.util.List;
 import java.util.PriorityQueue;
 
@@ -98,8 +97,13 @@ public final class Simulation {
             case DEPARTURE -> {
                 state.updateDeparture(time);
 
+                // Spawn unavailability if has unavailable time
                 this.addToFel(state.spawnUnavailableIfPossible(time, this.rng));
+
+                // Spawn departure if has requests and server is available
                 this.addToFel(state.spawnDepartureIfPossible(time, this.rng));
+
+                // Spawn arrival to self if is source node
                 this.addToFel(state.spawnArrivalIfPossilbe(time));
 
                 // Spawn arrival to child node if queue is not full otherwise drop
@@ -151,7 +155,7 @@ public final class Simulation {
      * @return a list of future events.
      */
     public List<Event> getFutureEventList() {
-        return new ArrayList<>(this.fel);
+        return List.copyOf(this.fel);
     }
 
     /**

src/main/java/net/berack/upo/valpre/sim/SimulationMultiple.java

@@ -1,5 +1,6 @@
 package net.berack.upo.valpre.sim;
 
+import java.io.PrintStream;
 import java.util.ArrayList;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executors;
@@ -99,16 +100,21 @@ public class SimulationMultiple {
      * Run the simulation multiple times with the given seed and end criteria. The
      * simulation runs will stop when the relative error of the confidence index is
      * less than the given value.
-     * The results are printed on the console.
+     * The results are printed on the PrintStream.
      * 
-     * @param seed      The seed to use for the random number generator.
-     * @param criterias The criteria to determine when to end the simulation. If
-     *                  null then the simulation will run until there are no more
-     *                  events.
+     * @param seed        The seed to use for the random number generator.
+     * @param runs        The maximum number of runs to perform.
+     * @param stream      The PrintStream to print the results.
+     * @param confidences The confidence indices to use to determine when to stop
+     *                    the simulation.
+     * @param criterias   The criteria to determine when to end the simulation. If
+     *                    null then the simulation will run until there are no more
+     *                    events.
      * @return The statistics the network.
      * @throws IllegalArgumentException If the confidence is not set.
      */
-    public Result.Summary runIncremental(long seed, int runs, ConfidenceIndices confidences, EndCriteria... criterias) {
+    public Result.Summary runIncremental(long seed, int runs, PrintStream stream, ConfidenceIndices confidences,
+            EndCriteria... criterias) {
         if (confidences == null)
             throw new IllegalArgumentException("Confidence must be not null");
 
@@ -116,7 +122,8 @@ public class SimulationMultiple {
         var results = new Result.Summary(rng.getSeed(), nodes);
         var output = new StringBuilder();
         var stop = false;
-        for (int i = 0; !stop; i++) {
+
+        for (int i = 0; !stop && runs > i; i++) {
             var sim = new Simulation(this.net, rng, criterias);
             var result = sim.run();
             results.add(result);
@@ -132,11 +139,11 @@ public class SimulationMultiple {
                 var oneSting = String.join("], [", errString);
 
                 output.append('[').append(oneSting).append("]");
-                System.out.print(output);
+                stream.print(output);
             }
         }
 
-        System.out.println(); // remove last printed line
+        stream.println(); // remove last printed line
         return results;
     }
 

src/main/resources/example1.jsimg

@@ -0,0 +1,146 @@
+<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>
+<archive xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" name="example1.jsimg" timestamp="Thu Mar 13 11:14:34 CET 2025" xsi:noNamespaceSchemaLocation="Archive.xsd">
+    <sim disableStatisticStop="false" logDecimalSeparator="," logDelimiter=";" logPath="C:\Users\giaco\JMT\" logReplaceMode="0" maxEvents="-1" maxSamples="1000000" name="example1.jsimg" polling="1.0" xsi:noNamespaceSchemaLocation="SIMmodeldefinition.xsd">
+        <userClass name="Class1" priority="0" referenceSource="Source " softDeadline="0.0" type="open"/>
+        <node name="Source ">
+            <section className="RandomSource">
+                <parameter array="true" classPath="jmt.engine.NetStrategies.ServiceStrategy" name="ServiceStrategy">
+                    <refClass>Class1</refClass>
+                    <subParameter classPath="jmt.engine.NetStrategies.ServiceStrategies.ServiceTimeStrategy" name="ServiceTimeStrategy">
+                        <subParameter classPath="jmt.engine.random.Exponential" name="Exponential"/>
+                        <subParameter classPath="jmt.engine.random.ExponentialPar" name="distrPar">
+                            <subParameter classPath="java.lang.Double" name="lambda">
+                                <value>0.2222222222222222</value>
+                            </subParameter>
+                        </subParameter>
+                    </subParameter>
+                </parameter>
+            </section>
+            <section className="ServiceTunnel"/>
+            <section className="Router">
+                <parameter array="true" classPath="jmt.engine.NetStrategies.RoutingStrategy" name="RoutingStrategy">
+                    <refClass>Class1</refClass>
+                    <subParameter classPath="jmt.engine.NetStrategies.RoutingStrategies.RandomStrategy" name="Random"/>
+                </parameter>
+            </section>
+        </node>
+        <node name="Sink">
+            <section className="JobSink"/>
+        </node>
+        <node name="Queue">
+            <classSoftDeadlines>
+                <softDeadline>0.0</softDeadline>
+            </classSoftDeadlines>
+            <quantumSize>
+                <quantaSize>0.0</quantaSize>
+            </quantumSize>
+            <quantumSwitchoverTime>
+                <quantumSwitchoverTime>0.0</quantumSwitchoverTime>
+            </quantumSwitchoverTime>
+            <section className="Queue">
+                <parameter classPath="java.lang.Integer" name="size">
+                    <value>-1</value>
+                </parameter>
+                <parameter array="true" classPath="java.lang.String" name="dropStrategies">
+                    <refClass>Class1</refClass>
+                    <subParameter classPath="java.lang.String" name="dropStrategy">
+                        <value>drop</value>
+                    </subParameter>
+                </parameter>
+                <parameter classPath="jmt.engine.NetStrategies.QueueGetStrategies.FCFSstrategy" name="FCFSstrategy"/>
+                <parameter array="true" classPath="jmt.engine.NetStrategies.QueuePutStrategy" name="QueuePutStrategy">
+                    <refClass>Class1</refClass>
+                    <subParameter classPath="jmt.engine.NetStrategies.QueuePutStrategies.TailStrategy" name="TailStrategy"/>
+                </parameter>
+            </section>
+            <section className="Server">
+                <parameter classPath="java.lang.Integer" name="maxJobs">
+                    <value>1</value>
+                </parameter>
+                <parameter array="true" classPath="java.lang.Integer" name="numberOfVisits">
+                    <refClass>Class1</refClass>
+                    <subParameter classPath="java.lang.Integer" name="numberOfVisits">
+                        <value>1</value>
+                    </subParameter>
+                </parameter>
+                <parameter array="true" classPath="jmt.engine.NetStrategies.ServiceStrategy" name="ServiceStrategy">
+                    <refClass>Class1</refClass>
+                    <subParameter classPath="jmt.engine.NetStrategies.ServiceStrategies.ServiceTimeStrategy" name="ServiceTimeStrategy">
+                        <subParameter classPath="jmt.engine.random.Normal" name="Normal"/>
+                        <subParameter classPath="jmt.engine.random.NormalPar" name="distrPar">
+                            <subParameter classPath="java.lang.Double" name="mean">
+                                <value>3.2</value>
+                            </subParameter>
+                            <subParameter classPath="java.lang.Double" name="standardDeviation">
+                                <value>0.6000000000000001</value>
+                            </subParameter>
+                        </subParameter>
+                    </subParameter>
+                </parameter>
+                <parameter array="true" classPath="java.lang.Integer" name="classParallelism">
+                    <refClass>Class1</refClass>
+                    <subParameter classPath="java.lang.Integer" name="serverParallelism">
+                        <value>1</value>
+                    </subParameter>
+                </parameter>
+                <parameter array="true" classPath="java.lang.String" name="serverNames">
+                    <subParameter classPath="java.lang.String" name="serverTypesNames">
+                        <value>Queue - Server Type 1</value>
+                    </subParameter>
+                </parameter>
+                <parameter array="true" classPath="java.lang.Integer" name="serversPerServerType">
+                    <subParameter classPath="java.lang.Integer" name="serverTypesNumOfServers">
+                        <value>1</value>
+                    </subParameter>
+                </parameter>
+                <parameter array="true" classPath="java.lang.Object" name="serverCompatibilities">
+                    <subParameter array="true" classPath="java.lang.Boolean" name="serverTypesCompatibilities">
+                        <subParameter classPath="java.lang.Boolean" name="compatibilities">
+                            <value>true</value>
+                        </subParameter>
+                    </subParameter>
+                </parameter>
+                <parameter classPath="java.lang.String" name="schedulingPolicy">
+                    <value>ALIS (Assign Longest Idle Server)</value>
+                </parameter>
+            </section>
+            <section className="Router">
+                <parameter array="true" classPath="jmt.engine.NetStrategies.RoutingStrategy" name="RoutingStrategy">
+                    <refClass>Class1</refClass>
+                    <subParameter classPath="jmt.engine.NetStrategies.RoutingStrategies.RandomStrategy" name="Random"/>
+                </parameter>
+            </section>
+        </node>
+        <measure alpha="0.01" name="Queue_Class1_Response Time" nodeType="station" precision="0.03" referenceNode="Queue" referenceUserClass="Class1" type="Response Time" verbose="false"/>
+        <measure alpha="0.01" name="Queue_Class1_Utilization" nodeType="station" precision="0.03" referenceNode="Queue" referenceUserClass="Class1" type="Utilization" verbose="false"/>
+        <measure alpha="0.01" name="Queue_Class1_Throughput" nodeType="station" precision="0.03" referenceNode="Queue" referenceUserClass="Class1" type="Throughput" verbose="false"/>
+        <connection source="Source " target="Queue"/>
+        <connection source="Queue" target="Sink"/>
+    </sim>
+    <jmodel xsi:noNamespaceSchemaLocation="JModelGUI.xsd">
+        <userClass color="#FF0000FF" name="Class1"/>
+        <station name="Source ">
+            <position angle="0.0" rotate="false" x="73.0" y="139.0"/>
+        </station>
+        <station name="Sink">
+            <position angle="0.0" rotate="false" x="354.0" y="139.0"/>
+        </station>
+        <station name="Queue">
+            <position angle="0.0" rotate="false" x="191.0" y="136.0"/>
+        </station>
+    </jmodel>
+    <results elapsedTime="932" logDecimalSeparator="," logDelimiter=";" pollingInterval="1.0" xsi:noNamespaceSchemaLocation="Results.xsd">
+        <measure alpha="0.99" analyzedSamples="245760" discardedSamples="390" finalValue="7.30224421202774" name="Queue_Class1_Response Time" nodeType="station" precision="0.03" referenceClass="Class1" referenceStation="Queue" state="1" type="2">
+            <sample lastIntervalAvgValue="7.171346385053164" lowerBound="6.925342616994286" meanValue="7.2654952908722095" simulationTime="349360.1710046531" upperBound="7.6056479647501325"/>
+            <sample lastIntervalAvgValue="7.340886944129393" lowerBound="7.145587638668616" meanValue="7.30224421202774" simulationTime="1105542.162869484" upperBound="7.458900785386865"/>
+        </measure>
+        <measure alpha="0.99" analyzedSamples="56320" discardedSamples="1755" finalValue="0.7110892727677632" name="Queue_Class1_Utilization" nodeType="station" precision="0.03" referenceClass="Class1" referenceStation="Queue" state="1" type="6">
+            <sample lastIntervalAvgValue="0.7121434625959978" lowerBound="0.6959357730746889" meanValue="0.7110892727677632" simulationTime="202809.54195132584" upperBound="0.7262427724608376"/>
+            <sample lastIntervalAvgValue="0.7121434625959978" lowerBound="0.6959357730746889" meanValue="0.7110892727677632" simulationTime="202809.54195132584" upperBound="0.7262427724608376"/>
+        </measure>
+        <measure alpha="0.99" analyzedSamples="51200" discardedSamples="180" finalValue="0.22256617058473832" name="Queue_Class1_Throughput" nodeType="station" precision="0.03" referenceClass="Class1" referenceStation="Queue" state="1" type="5">
+            <sample lastIntervalAvgValue="0.22277397312289457" lowerBound="0.21822871906729738" meanValue="0.22256617058473832" simulationTime="230637.3553415772" upperBound="0.22707953845333897"/>
+            <sample lastIntervalAvgValue="0.22277397312289457" lowerBound="0.21822871906729738" meanValue="0.22256617058473832" simulationTime="230637.3553415772" upperBound="0.22707953845333897"/>
+        </measure>
+    </results>
+</archive>

src/test/java/net/berack/upo/valpre/sim/TestInteractions.java

@@ -0,0 +1,187 @@
+package net.berack.upo.valpre.sim;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.ByteArrayInputStream;
+import java.io.OutputStream;
+import java.io.PrintStream;
+
+import org.junit.Test;
+
+import net.berack.upo.valpre.InteractiveConsole;
+import net.berack.upo.valpre.rand.Distribution;
+
+public class TestInteractions {
+
+    @Test
+    public void distributionToString() throws Exception {
+        var exp = new Distribution.Exponential(1.0);
+        assertEquals("Exponential(1.0)", Distribution.toString(exp));
+
+        var uniform = new Distribution.Uniform(0.0, 1.0);
+        assertEquals("Uniform(0.0, 1.0)", Distribution.toString(uniform));
+
+        var erlang = new Distribution.Erlang(2, 1.0);
+        assertEquals("Erlang(2, 1.0)", Distribution.toString(erlang));
+
+        var normal = new Distribution.Normal(3.2, 0.6);
+        assertEquals("Normal(3.2, 0.6)", Distribution.toString(normal));
+
+        var normalBoxMuller = new Distribution.NormalBoxMuller(3.2, 0.6);
+        assertEquals("NormalBoxMuller(3.2, 0.6)", Distribution.toString(normalBoxMuller));
+
+        var unavailable = new Distribution.UnavailableTime(0.1, exp);
+        assertEquals("UnavailableTime(0.1, Exponential(1.0))", Distribution.toString(unavailable));
+    }
+
+    @Test
+    public void nodeToString() {
+        var exp = new Distribution.Exponential(1.0);
+        var normal = new Distribution.Normal(3.2, 0.6);
+        var unavailable = new Distribution.UnavailableTime(0.1, exp);
+
+        var node = new ServerNode.Builder("Source", exp).build();
+        assertEquals("Source[servers:1, queue:100, spawn:0, Exponential(1.0)]", node.toString());
+
+        node = new ServerNode.Builder("Queue", normal).build();
+        assertEquals("Queue[servers:1, queue:100, spawn:0, Normal(3.2, 0.6)]", node.toString());
+
+        node = new ServerNode.Builder("Queue", normal).queue(10).servers(5).spawn(100).build();
+        assertEquals("Queue[servers:5, queue:10, spawn:100, Normal(3.2, 0.6)]", node.toString());
+
+        node = new ServerNode.Builder("Queue", normal).queue(10).servers(5).spawn(100).unavailable(unavailable).build();
+        assertEquals(
+                "Queue[servers:5, queue:10, spawn:100, Normal(3.2, 0.6), u:UnavailableTime(0.1, Exponential(1.0))]",
+                node.toString());
+    }
+
+    @Test
+    public void netToString() {
+        var net = new Net();
+        assertEquals("", net.toString());
+
+        var node1 = new ServerNode.Builder("Source", new Distribution.Exponential(1)).build();
+        net.addNode(node1);
+        assertEquals(node1 + " -\n", net.toString());
+
+        var node2 = new ServerNode.Builder("Server", new Distribution.Normal(3.2, 0.6)).build();
+        net.addNode(node2);
+        assertEquals(node1 + " -\n" + node2 + " -\n", net.toString());
+
+        net.addConnection(0, 1, 1.0);
+        assertEquals(node1 + " -> Server(1.0)\n" + node2 + " -\n", net.toString());
+
+        var node3 = new ServerNode.Builder("Server2", new Distribution.Normal(4.1, 0.1)).build();
+        net.addNode(node3);
+        assertEquals(node1 + " -> Server(1.0)\n" + node2 + " -\n" + node3 + " -\n", net.toString());
+
+        net.addConnection(0, 2, 1.0);
+        net.normalizeWeights();
+        assertEquals(node1 + " -> Server(0.5), Server2(0.5)\n" + node2 + " -\n" + node3 + " -\n", net.toString());
+
+        net.addConnection(1, 2, 1.0);
+        assertEquals(node1 + " -> Server(0.5), Server2(0.5)\n"
+                + node2 + " -> Server2(1.0)\n"
+                + node3 + " -\n",
+                net.toString());
+
+        var const0 = new Distribution.Uniform(0, 0);
+        var unavailable = new Distribution.UnavailableTime(0.1, new Distribution.Exponential(1));
+        var other = ServerNode.Builder.queue("Other", 1, const0, unavailable);
+        net.addNode(other);
+        assertEquals(node1 + " -> Server(0.5), Server2(0.5)\n"
+                + node2 + " -> Server2(1.0)\n"
+                + node3 + " -\n"
+                + other + " -\n",
+                net.toString());
+    }
+
+    @Test(timeout = 1000)
+    public void netBuilderInteractive() {
+
+        // Test the interactive console EXIT
+        var net = runInteraction("7");
+        assertEquals("", net.toString());
+
+        // Test the interactive console ADD NODE
+        net = runInteraction("1", "1", "Source", "1", "1.0", "7");
+        assertEquals("Source[servers:1, queue:100, spawn:-1, Exponential(1.0)] -\n", net.toString());
+
+        // Test the interactive console ADD SECOND NODE
+        net = runInteraction("1", "2", "Terminal", "1", "2.0", "500",
+                "1", "3", "Queue", "5", "3.2", "0.6", "1",
+                "7");
+        assertEquals("Terminal[servers:1, queue:100, spawn:500, Exponential(2.0)] -\n"
+                + "Queue[servers:1, queue:100, spawn:0, Normal(3.2, 0.6)] -\n", net.toString());
+
+        // Test the interactive console ADD CONNECTION
+        net = runInteraction("1", "1", "Source", "1", "2.0",
+                "1", "3", "Queue", "5", "3.2", "0.6", "1",
+                "2", "Source", "Queue", "1.0",
+                "7");
+        assertEquals("Source[servers:1, queue:100, spawn:-1, Exponential(2.0)] -> Queue(1.0)\n"
+                + "Queue[servers:1, queue:100, spawn:0, Normal(3.2, 0.6)] -\n", net.toString());
+
+        // Test the interactive console CLEAR
+        net = runInteraction("1", "1", "Source", "1", "2.0",
+                "1", "3", "Queue", "5", "3.2", "0.6", "1",
+                "2", "Source", "Queue", "1.0",
+                "2", "Queue", "Queue", "1.0",
+                "5", "7");
+        assertEquals("", net.toString());
+
+        // Test the interactive console LOAD
+        net = runInteraction("4", "1", "src/test/resources/example1.net", "7");
+        assertEquals("Source[servers:1, queue:100, spawn:10000, Exponential(0.2222222222222222)] -> Queue(1.0)\n"
+                + "Queue[servers:1, queue:100, spawn:0, NormalBoxMuller(3.2, 0.6)] -\n",
+                net.toString());
+
+        // Test the interactive console LOAD EXAMPLE 1
+        net = runInteraction("4", "2", "1", "7");
+        assertEquals("Source[servers:1, queue:100, spawn:10000, Exponential(0.2222222222222222)] -> Queue(1.0)\n"
+                + "Queue[servers:1, queue:100, spawn:0, NormalBoxMuller(3.2, 0.6)] -\n",
+                net.toString());
+
+        // Test the interactive console LOAD EXAMPLE 2
+        net = runInteraction("4", "2", "2", "7");
+        assertEquals("Source[servers:1, queue:100, spawn:10000, Exponential(1.5)] -> Service1(1.0)\n"
+                + "Service1[servers:1, queue:100, spawn:0, Exponential(2.0)] -> Service2(1.0)\n"
+                + "Service2[servers:1, queue:100, spawn:0, Exponential(3.5), u:UnavailableTime(0.1, Exponential(10.0))] -\n",
+                net.toString());
+    }
+
+    private static Net runInteraction(String... commands) {
+        var out = new PrintStream(OutputStream.nullOutputStream());
+        var inputs = String.join("\n", commands);
+        var bytes = inputs.getBytes();
+        var in = new ByteArrayInputStream(bytes);
+        return new InteractiveConsole(out, in).run();
+    }
+
+    /*
+     * An interaction example is like this:
+     * 1. Add a node
+     * - Choose the type of node to create:
+     * - 1. Source
+     * - 2. Queue
+     * - 3. Queue with unavailable time
+     * - Node name: Name
+     * - Arrivals limit (0 for Int.Max) / Number of servers: 1
+     * - Choose the type of service distribution:
+     * - - 1. Exponential
+     * - - 2. Uniform
+     * - - 3. Erlang
+     * - - 4. UnavailableTime
+     * - - 5. Normal
+     * - - 6. NormalBoxMuller
+     * - - 7. None
+     * 2. Add a connection
+     * - Enter the source node: Source
+     * - Enter the target node: Queue
+     * - Enter the weight: 1.0
+     * 3. Save the net
+     * 4. Load net
+     * 5. Clear
+     * 6. Exit
+     */
+}

src/test/java/net/berack/upo/valpre/sim/TestSaveExamplesNet.java

@@ -4,6 +4,8 @@ import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 
 import java.io.IOException;
+import java.io.OutputStream;
+import java.io.PrintStream;
 import java.util.HashSet;
 import org.junit.Test;
 import org.junit.jupiter.api.AfterAll;
@@ -11,61 +13,26 @@ import org.junit.jupiter.api.BeforeAll;
 
 import com.esotericsoftware.kryo.KryoException;
 
+import net.berack.upo.valpre.NetExamples;
 import net.berack.upo.valpre.SimulationBuilder;
-import net.berack.upo.valpre.rand.Distribution;
 import net.berack.upo.valpre.rand.Rng;
 import net.berack.upo.valpre.sim.stats.CsvResult;
 import net.berack.upo.valpre.sim.stats.NodeStats;
 
 public class TestSaveExamplesNet {
 
-    private static final Distribution exp0_22 = new Distribution.Exponential(1.0 / 4.5);
-    private static final Distribution exp2 = new Distribution.Exponential(2.0);
-    private static final Distribution exp1_5 = new Distribution.Exponential(1.5);
-    private static final Distribution exp3_5 = new Distribution.Exponential(3.5);
-    private static final Distribution exp10 = new Distribution.Exponential(10.0);
-
-    private static final Distribution norm3_2 = new Distribution.NormalBoxMuller(3.2, 0.6);
-    private static final Distribution norm4_2 = new Distribution.NormalBoxMuller(4.2, 0.6);
-
-    private static final Distribution unNorm = new Distribution.UnavailableTime(0.2, norm4_2);
-    private static final Distribution unExp = new Distribution.UnavailableTime(0.1, exp10);
-
-    private static final int spawn = 10000;
-    private static final String path = "src/main/resources/example%d.%s";
+    private static final String path = "src/test/resources/example%d.%s";
     private static final String netFile1 = path.formatted(1, "net");
     private static final String netFile2 = path.formatted(2, "net");
-    private static final String netFile3 = path.formatted(3, "net");
     private static final String csv1 = path.formatted(1, "csv");
     private static final String csv2 = path.formatted(2, "csv");
-    private static final String csv3 = path.formatted(3, "csv");
-
-    private static final Net net1 = new Net();
-    private static final Net net2 = new Net();
-    private static final Net net3 = new Net();
-    static {
-        net1.addNode(ServerNode.Builder.sourceLimited("Source", spawn, exp0_22));
-        net1.addNode(ServerNode.Builder.queue("Queue", 1, norm3_2));
-        net1.addConnection(0, 1, 1.0);
-
-        net2.addNode(ServerNode.Builder.sourceLimited("Source", spawn, exp0_22));
-        net2.addNode(ServerNode.Builder.queue("Queue", 1, norm3_2));
-        net2.addNode(ServerNode.Builder.queue("Queue Wait", 1, norm3_2, unNorm));
-        net2.addConnection(0, 1, 1.0);
-        net2.addConnection(1, 2, 1.0);
-
-        net3.addNode(ServerNode.Builder.sourceLimited("Source", spawn, exp1_5));
-        net3.addNode(ServerNode.Builder.queue("Service1", 1, exp2));
-        net3.addNode(ServerNode.Builder.queue("Service2", 1, exp3_5, unExp));
-        net3.addConnection(0, 1, 1.0);
-        net3.addConnection(1, 2, 1.0);
-    }
+    private static final Net net1 = NetExamples.getNet1();
+    private static final Net net2 = NetExamples.getNet2();
 
     @BeforeAll
     public void saveAll() throws IOException {
         net1.save(netFile1);
         net2.save(netFile2);
-        net3.save(netFile3);
     }
 
     @Test
@@ -85,20 +52,6 @@ public class TestSaveExamplesNet {
     public void loadExample2() throws KryoException, IOException {
         var sim = new Simulation(Net.load(netFile2), new Rng());
         var res = sim.run();
-        var time = 45417.0;
-        var maxErr = time / 1000.0;
-
-        assertEquals(Rng.DEFAULT, res.seed);
-        assertEquals(time, res.simulationTime, maxErr);
-        testNode(res.getStat("Source"), 10000, time, 1.0, 4.5, 0.0, 0.0);
-        testNode(res.getStat("Queue"), 10000, time, 2.6, 7.2, 4.0, 0.0);
-        testNode(res.getStat("Queue Wait"), 10000, time, 5.8, 22.3, 19.1, 8497.7);
-    }
-
-    @Test
-    public void loadExample3() throws KryoException, IOException {
-        var sim = new Simulation(Net.load(netFile3), new Rng());
-        var res = sim.run();
         var time = 6736.0;
         var maxErr = time / 1000.0;
 
@@ -153,33 +106,26 @@ public class TestSaveExamplesNet {
     @Test
     @AfterAll
     public void multiSimulation1() throws Exception {
-        new SimulationBuilder(net1)
-                .setCsv(csv1)
-                .setMaxRuns(1000)
-                .setSeed(2007539552L)
-                .setParallel(true)
-                .run();
+        try (var newOut = new PrintStream(OutputStream.nullOutputStream())) {
+            new SimulationBuilder(net1)
+                    .setCsv(csv1)
+                    .setMaxRuns(1000)
+                    .setSeed(2007539552L)
+                    .setParallel(true)
+                    .run(newOut);
+        }
     }
 
     @Test
     @AfterAll
     public void multiSimulation2() throws Exception {
-        new SimulationBuilder(net2)
-                .setCsv(csv2)
-                .setMaxRuns(1000)
-                .setSeed(2007539552L)
-                .setParallel(true)
-                .run();
-    }
-
-    @Test
-    @AfterAll
-    public void multiSimulation3() throws Exception {
-        new SimulationBuilder(net3)
-                .setCsv(csv3)
-                .setMaxRuns(1000)
-                .setSeed(2007539552L)
-                .setParallel(true)
-                .run();
+        try (var newOut = new PrintStream(OutputStream.nullOutputStream())) {
+            new SimulationBuilder(net2)
+                    .setCsv(csv2)
+                    .setMaxRuns(1000)
+                    .setSeed(2007539552L)
+                    .setParallel(true)
+                    .run(newOut);
+        }
     }
 }

src/test/java/net/berack/upo/valpre/sim/TestSimulation.java

@@ -5,6 +5,7 @@ import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import java.util.HashSet;
 
@@ -23,7 +24,7 @@ public class TestSimulation {
     private static final ServerNode node0;
     private static final ServerNode node1;
     static {
-        node0 = ServerNode.Builder.sourceLimited("First", 0, const1);
+        node0 = ServerNode.Builder.terminal("First", 0, const1);
         node1 = ServerNode.Builder.queue("Second", 1, const1);
 
         simpleNet = new Net();
@@ -56,10 +57,10 @@ public class TestSimulation {
         node = ServerNode.Builder.source("Source", const1);
         assertEquals("Source", node.name);
         assertEquals(1, node.maxServers);
-        assertEquals(Integer.MAX_VALUE, node.spawnArrivals);
+        assertEquals(-1, node.spawnArrivals);
         assertEquals(1.0, node.getServiceTime(null), DELTA);
 
-        node = ServerNode.Builder.sourceLimited("Source", 50, const1);
+        node = ServerNode.Builder.terminal("Source", 50, const1);
         assertEquals("Source", node.name);
         assertEquals(1, node.maxServers);
         assertEquals(50, node.spawnArrivals);
@@ -196,7 +197,7 @@ public class TestSimulation {
     @Test
     public void nodeStatsUpdates() {
         var net = new Net();
-        net.addNode(ServerNode.Builder.sourceLimited("Source", 50, const1));
+        net.addNode(ServerNode.Builder.terminal("Source", 50, const1));
         net.addNode(node1);
         net.addConnection(0, 1, 1.0);
 
@@ -393,13 +394,23 @@ public class TestSimulation {
 
     @Test
     public void simulation() {
-        var start = System.nanoTime();
+        assertThrows(NullPointerException.class, () -> new Simulation(null, rigged));
+        assertThrows(NullPointerException.class, () -> new Simulation(simpleNet, null));
+
         var sim = new Simulation(simpleNet, rigged);
+        assertTrue(sim.hasEnded());
+        assertEquals(0, sim.getEventsProcessed());
+        assertEquals(0.0, sim.getTime(), DELTA);
+        var fel = sim.getFutureEventList();
+        assertEquals(0, fel.size());
+
+        var start = System.nanoTime();
+        sim = new Simulation(simpleNet, rigged);
         // knowing that it takes time to allocate the object
         // we can use the average time
         var endAllocation = System.nanoTime();
         var time = (endAllocation + start) / 2;
-        var diff = 0.5e-6 * (endAllocation - start); // getting the error margin in ms
+        var diff = 1e-6 * (endAllocation - start); // getting the error margin in ms
 
         assertTrue(sim.hasEnded());
         assertEquals(0, sim.getEventsProcessed());
@@ -410,7 +421,7 @@ public class TestSimulation {
         assertEquals(0, sim.getNodeState(node0.name).numServerUnavailable);
         assertEquals(0, sim.getNodeState(node1.name).numServerBusy);
         assertEquals(0, sim.getNodeState(node1.name).numServerUnavailable);
-        var fel = sim.getFutureEventList();
+        fel = sim.getFutureEventList();
         assertEquals(0, fel.size());
 
         sim.addToFel(Event.newArrival(0, sim.getTime()));
@@ -489,6 +500,8 @@ public class TestSimulation {
         assertEquals(0, sim.getNodeState(node1.name).numServerUnavailable);
         fel = sim.getFutureEventList();
         assertEquals(0, fel.size());
+        final var s = sim;
+        assertThrows(NullPointerException.class, () -> s.processNextEvent());
 
         var elapsed = (double) (System.nanoTime() - time);
         var result = sim.endSimulation();
@@ -529,7 +542,7 @@ public class TestSimulation {
     @Test
     public void simulationStats() {
         var net = new Net();
-        net.addNode(ServerNode.Builder.sourceLimited("Source", 50, const1));
+        net.addNode(ServerNode.Builder.terminal("Source", 50, const1));
 
         var sim = new Simulation(net, rigged);
         var result = sim.run();
@@ -581,7 +594,7 @@ public class TestSimulation {
     @Test
     public void simulationDrop() {
         var net = new Net();
-        net.addNode(ServerNode.Builder.sourceLimited("Source", 50, const1));
+        net.addNode(ServerNode.Builder.terminal("Source", 50, const1));
         net.addNode(new ServerNode.Builder("Queue", _ -> 2.0).queue(20).build());
         net.addConnection(0, 1, 1.0);