Vorlesung 14 / Aufgabe 1

README.md

@@ -6,6 +6,5 @@ Lösungen zu den Aufgaben der Vorlesung "Programmieren" des ersten und zweiten S
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VL14/Aufgabe01/Aufgabe01.java

@@ -0,0 +1,18 @@
+package VL14.Aufgabe01;
+
+/**
+ * Vorlesung 14 / Aufgabe 1
+ *
+ * @author Sebastian Brosch
+ */
+class Aufgabe01 {
+
+  public static void main(String[] args) {
+    Counter counterUp = new Counter("T1", 1, 100);
+    Counter counterDown = new Counter("T2", -10);
+    Thread threadCounterUp = new Thread(counterUp);
+    Thread threadCounterDown = new Thread(counterDown);
+    threadCounterUp.start();
+    threadCounterDown.start();
+  }
+}

VL14/Aufgabe01/Counter.java

@@ -0,0 +1,56 @@
+package VL14.Aufgabe01;
+
+/**
+ * Class representing a counter.
+ *
+ * @author Sebastian Brosch
+ */
+public class Counter implements Runnable {
+  static int counter;
+
+  // some information of the counter.
+  private int number;
+  private String name;
+
+  /**
+   * Create a new counter with initializing the start value.
+   *
+   * @param name   The name of the counter.
+   * @param number The number to increment or decrement the counter.
+   * @param start  The start value of the counter.
+   */
+  public Counter(String name, int number, int start) {
+    this(name, number);
+    counter = start;
+  }
+
+  /**
+   * Create a new counter without initializing the start value.
+   *
+   * @param name   The name of the counter.
+   * @param number The number to increment or decrement the counter.
+   */
+  public Counter(String name, int number) {
+    this.number = number;
+    this.name = name;
+  }
+
+  /**
+   * Method to run some code in a Thread.
+   */
+  public void run() {
+    while (counter > 0 && counter < 1000) {
+      this.count();
+    }
+  }
+
+  /**
+   * Method to increment or decrement the counter.
+   */
+  private void count() {
+    synchronized (getClass()) {
+      counter += this.number;
+      System.out.printf("%3d [%s: %3d]\n", counter, this.name, this.number);
+    }
+  }
+}

VL14/Aufgabe02/Aufgabe02.java

@@ -0,0 +1,27 @@
+package VL14.Aufgabe02;
+
+/**
+ * Vorlesung 14 / Aufgabe 2
+ *
+ * @author Sebastian Brosch
+ */
+public class Aufgabe02 {
+  public static void main(String[] args) {
+    final int NUMBER_OF_USERS = 5;
+    final int NUMBER_OF_PRINTERS = 2;
+
+    // create some users.
+    for (int u = 0; u < NUMBER_OF_USERS; u++) {
+      User user = new User();
+      Thread threadUser = new Thread(user);
+      threadUser.start();
+    }
+
+    // create some printers.
+    for (int p = 0; p < NUMBER_OF_PRINTERS; p++) {
+      Printer printer = new Printer();
+      Thread threadPrinter = new Thread(printer);
+      threadPrinter.start();
+    }
+  }
+}

VL14/Aufgabe02/Printer.java

@@ -0,0 +1,23 @@
+package VL14.Aufgabe02;
+
+/**
+ * Class which represents a printer.
+ *
+ * @author Sebastian Brosch
+ */
+public class Printer implements Runnable {
+  public void run() {
+    while (true) {
+      synchronized (PrinterQueue.queue) {
+        if (PrinterQueue.queue.size() > 0) {
+          System.out.println(PrinterQueue.queue.poll());
+        }
+      }
+
+      try {
+        Thread.sleep(500);
+      } catch (InterruptedException e) {
+      }
+    }
+  }
+}

VL14/Aufgabe02/PrinterQueue.java

@@ -0,0 +1,12 @@
+package VL14.Aufgabe02;
+
+import java.util.LinkedList;
+
+/**
+ * Class which represents a printer queue.
+ *
+ * @author Sebastian Brosch
+ */
+public class PrinterQueue {
+  static LinkedList<String> queue = new LinkedList<String>();
+}

VL14/Aufgabe02/User.java

@@ -0,0 +1,23 @@
+package VL14.Aufgabe02;
+
+/**
+ * Class which represents a user.
+ *
+ * @author Sebastian Brosch
+ */
+public class User implements Runnable {
+  private int number = 0;
+
+  public void run() {
+    while (true) {
+      synchronized (PrinterQueue.queue) {
+        PrinterQueue.queue.add(Thread.currentThread().getName() + ": " + this.number++);
+      }
+
+      try {
+        Thread.sleep(100);
+      } catch (InterruptedException e) {
+      }
+    }
+  }
+}