Merge pull request #5428 from vaibs28/master

BAEL-2188 Print even and odd numbers using 2 threads

core-java-concurrency/src/main/java/com/baeldung/concurrent/evenandodd/PrintEvenOdd.java

@@ -0,0 +1,72 @@
+package com.baeldung.concurrent.evenandodd;
+
+public class PrintEvenOdd {
+
+    public static void main(String... args) {
+        Printer print = new Printer();
+        Thread t1 = new Thread(new TaskEvenOdd(print, 10, false));
+        t1.setName("Odd");
+        Thread t2 = new Thread(new TaskEvenOdd(print, 10, true));
+        t2.setName("Even");
+        t1.start();
+        t2.start();
+    }
+}
+
+class TaskEvenOdd implements Runnable {
+    private int max;
+    private Printer print;
+    private boolean isEvenNumber;
+
+    TaskEvenOdd(Printer print, int max, boolean isEvenNumber) {
+        this.print = print;
+        this.max = max;
+        this.isEvenNumber = isEvenNumber;
+    }
+
+    @Override
+    public void run() {
+        int number = isEvenNumber == true ? 2 : 1;
+        while (number <= max) {
+            if (isEvenNumber) {
+                print.printEven(number);
+            } else {
+                print.printOdd(number);
+            }
+            number += 2;
+        }
+    }
+}
+
+class Printer {
+    boolean isOdd = false;
+
+    synchronized void printEven(int number) {
+        while (isOdd == false) {
+            try {
+                wait();
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+        }
+        System.out.println(Thread.currentThread()
+            .getName() + ":" + number);
+        isOdd = false;
+        notify();
+    }
+
+    synchronized void printOdd(int number) {
+        while (isOdd == true) {
+            try {
+                wait();
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+        }
+        System.out.println(Thread.currentThread()
+            .getName() + ":" + number);
+        isOdd = true;
+        notify();
+    }
+
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/evenandodd/SemaphoreDemo.java

@@ -0,0 +1,83 @@
+package com.baeldung.concurrent.evenandodd;
+
+import java.util.concurrent.Semaphore;
+
+public class SemaphoreDemo {
+
+    public static void main(String[] args) {
+
+        SharedPrinter sp = new SharedPrinter();
+        Thread odd = new Thread(new Odd(sp, 10));
+        odd.setName("Odd");
+        Thread even = new Thread(new Even(sp, 10));
+        even.setName("Even");
+
+        odd.start();
+        even.start();
+
+    }
+
+}
+
+class SharedPrinter {
+
+    Semaphore semEven = new Semaphore(0);
+    Semaphore semOdd = new Semaphore(1);
+
+    public void printEvenNum(int num) {
+        try {
+            semEven.acquire();
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+        System.out.println(Thread.currentThread()
+            .getName() + ":"+num);
+        semOdd.release();
+    }
+
+    public void printOddNum(int num) {
+        try {
+            semOdd.acquire();
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+        System.out.println(Thread.currentThread()
+            .getName() + ":"+ num);
+        semEven.release();
+
+    }
+}
+
+class Even implements Runnable {
+    SharedPrinter sp;
+    int max;
+
+    Even(SharedPrinter sp, int max) {
+        this.sp = sp;
+        this.max = max;
+    }
+
+    @Override
+    public void run() {
+        for (int i = 2; i <= max; i = i + 2) {
+            sp.printEvenNum(i);
+        }
+    }
+}
+
+class Odd implements Runnable {
+    SharedPrinter sp;
+    int max;
+
+    Odd(SharedPrinter sp, int max) {
+        this.sp = sp;
+        this.max = max;
+    }
+
+    @Override
+    public void run() {
+        for (int i = 1; i <= max; i = i + 2) {
+            sp.printOddNum(i);
+        }
+    }
+}