Initial commit

solutions-exercises/TrafficLIght/build.gradle

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+/*
+ * Gradle build configuration for specific lab module / exercise
+ * Default declarations can be found in the lab main build configuration (../../gradle.build)
+ * Declarations in this file extend or override the default values.
+ */
+// the Java plugin is added by default in the main lab configuration
+plugins {
+    // Apply the application plugin to add support for building a CLI application.
+    id 'application'
+}
+
+description = 'Lab04 TrafficLight Solution'
+
+dependencies {
+
+}
+
+// Configuration for Application plugin
+application {
+    // Define the main class for the application.
+    mainClass = 'ch.zhaw.prog2.trafficlight.TrafficLightOperation'
+}

solutions-exercises/TrafficLIght/src/main/java/ch/zhaw/prog2/trafficlight/Car.java

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+package ch.zhaw.prog2.trafficlight;
+
+import java.util.Random;
+
+class Car extends Thread {
+    private final TrafficLight[] trafficLights;
+    private int pos;
+
+    public Car(String name, TrafficLight[] trafficLights) {
+        super(name);
+        this.trafficLights = trafficLights;
+        pos = 0; // start at first light
+        start();
+    }
+
+    public synchronized int position() {
+        return pos;
+    }
+
+    private void gotoNextLight() {
+        pos = ++pos % trafficLights.length;
+    }
+
+    @Override
+    public void run() {
+        Random random = new Random();
+        while (true) {
+            try {
+                sleep(random.nextInt(500));
+            } catch (InterruptedException e) {
+                System.out.println(e.getMessage());
+            }
+            trafficLights[pos].passby();
+            gotoNextLight();
+        }
+    }
+}

solutions-exercises/TrafficLIght/src/main/java/ch/zhaw/prog2/trafficlight/TrafficLight.java

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+package ch.zhaw.prog2.trafficlight;
+
+class TrafficLight {
+    private boolean red;
+
+    public TrafficLight() {
+        red = true;
+    }
+
+    public synchronized void passby() {
+        while (red) {
+            try {
+                wait();
+            } catch (InterruptedException logOrIgnore) {
+                System.out.println(logOrIgnore.getMessage());
+            }
+        }
+    }
+
+    public synchronized void switchToRed() {
+        red = true;
+    }
+
+    public synchronized void switchToGreen() {
+        red = false;
+        notifyAll();
+    }
+}

solutions-exercises/TrafficLIght/src/main/java/ch/zhaw/prog2/trafficlight/TrafficLightOperation.java

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+package ch.zhaw.prog2.trafficlight;
+
+public class TrafficLightOperation {
+    private static volatile boolean running = true;
+
+    public static void terminate () {
+        running = false;
+    }
+
+    public static void main(String[] args) {
+        TrafficLight[] trafficLights = new TrafficLight[7];
+        Car[] cars = new Car[20];
+        for (int i = 0; i < trafficLights.length; i++)
+            trafficLights[i] = new TrafficLight();
+        for (int i = 0; i < cars.length; i++) {
+            cars[i] = new Car("Car " + i, trafficLights);
+        }
+
+        // Simulation
+        while (running) {
+            for (int greenIndex = 0; greenIndex < trafficLights.length; greenIndex = greenIndex + 2) {
+                // Display state of simulation
+                System.out.println("=====================================================");
+                for (int j = 0; j < trafficLights.length; j++) {
+                    String lightState;
+                    if (j == greenIndex || j == greenIndex + 1)
+                        lightState = "✅";
+                    else
+                        lightState = "🛑";
+                    System.out.print(lightState + " at Light " + j + ":");
+                    for (int carNumber = 0; carNumber < cars.length; carNumber++) {
+                        if (cars[carNumber].position() == j)
+                            System.out.print(" " + carNumber);
+                    }
+                    System.out.println();
+                }
+                System.out.println("=====================================================");
+                try {
+                    Thread.sleep(3000);
+                } catch (InterruptedException logOrIgnore) {
+                    System.out.println(logOrIgnore.getMessage());
+                }
+                trafficLights[greenIndex].switchToGreen();
+                if (greenIndex + 1 < trafficLights.length) {
+                    trafficLights[greenIndex + 1].switchToGreen();
+                }
+
+                // green period
+                try {
+                    Thread.sleep((int) (Math.random() * 500));
+                } catch (InterruptedException logOrIgnore) {
+                    System.out.println(logOrIgnore.getMessage());
+                }
+                trafficLights[greenIndex].switchToRed();
+                if (greenIndex + 1 < trafficLights.length)
+                    trafficLights[greenIndex + 1].switchToRed();
+
+                // red period
+                try {
+                    Thread.sleep(1000);
+                } catch (InterruptedException logOrIgnore) {
+                    System.out.println(logOrIgnore.getMessage());
+                }
+            }
+        }
+    }
+}