CountDownLatch and CyclicBarrier example

Author: serdaralkancode

src/main/java/tr/salkan/code/java/threadExecutor/example/threads/countDownLatch/Example.java

@@ -0,0 +1,60 @@
+package tr.salkan.code.java.threadExecutor.example.threads.countDownLatch;
+
+import java.util.concurrent.CountDownLatch;
+
+public class Example {
+
+    public static void main(String[] args) throws InterruptedException {
+
+        CountDownLatch latch = new CountDownLatch(4);
+
+        ThreadExample first = new ThreadExample(1000, latch,
+                "ThreadExample-1");
+        ThreadExample second = new ThreadExample(2000, latch,
+                "ThreadExample-2");
+        ThreadExample third = new ThreadExample(3000, latch,
+                "ThreadExample-3");
+        ThreadExample fourth = new ThreadExample(4000, latch,
+                "ThreadExample-4");
+
+        fourth.start();
+        third.start();
+        second.start();
+        first.start();
+
+        latch.await();
+
+        System.out.println(Thread.currentThread().getName() +
+                " has finished");
+    }
+}
+
+class ThreadExample extends Thread
+{
+    private int delay;
+    private CountDownLatch latch;
+
+    public ThreadExample(int delay, CountDownLatch latch,
+                  String name)
+    {
+        super(name);
+        this.delay = delay;
+        this.latch = latch;
+    }
+
+    @Override
+    public void run()
+    {
+        try
+        {
+            Thread.sleep(delay);
+            latch.countDown();
+            System.out.println(Thread.currentThread().getName()
+                    + " finished");
+        }
+        catch (InterruptedException e)
+        {
+            e.printStackTrace();
+        }
+    }
+}

src/main/java/tr/salkan/code/java/threadExecutor/example/threads/countDownLatch/note.txt

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+CountDownLatch -> Java 1.5
+
+But using
+
+CompletableFuture
+
+**** CompletableFuture.allOf(future1,future2)
+
+      or
+
+     future1.thenAcceptBothAsync(future2, (x,y) -> System.out.println("Result = " + (x + y))

src/main/java/tr/salkan/code/java/threadExecutor/example/threads/cyclicBarrier/CyclicBarrierFinishEvent.java

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+package tr.salkan.code.java.threadExecutor.example.threads.cyclicBarrier;
+
+public class CyclicBarrierFinishEvent implements Runnable{
+
+    public void run() {
+
+        System.out.println("As 3 threads have reached common barrier point "
+                + ", CyclicBarrrierFinishEvent has been triggered");
+        System.out.println("You can update shared variables if any");
+    }
+
+}

src/main/java/tr/salkan/code/java/threadExecutor/example/threads/cyclicBarrier/Example.java

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+package tr.salkan.code.java.threadExecutor.example.threads.cyclicBarrier;
+
+import java.util.concurrent.CyclicBarrier;
+
+public class Example {
+
+    public static void main(String[] args) {
+
+        CyclicBarrier cyclicBarrier=new CyclicBarrier(3 ,new CyclicBarrierFinishEvent());
+
+        RunnableTaskExample runnableTask1=new RunnableTaskExample(cyclicBarrier,1000);
+        RunnableTaskExample runnableTask2=new RunnableTaskExample(cyclicBarrier,2000);
+        RunnableTaskExample runnableTask3=new RunnableTaskExample(cyclicBarrier,3000);
+
+
+        //Create and start 3 threads
+        new Thread(runnableTask1,"Thread-1").start();
+        new Thread(runnableTask2,"Thread-2").start();
+        new Thread(runnableTask3,"Thread-3").start();
+
+        /*
+         * We are reusing cyclic barrier using below threads
+         * */
+        RunnableTaskExample runnableTask4=new RunnableTaskExample(cyclicBarrier,4000);
+        RunnableTaskExample runnableTask5=new RunnableTaskExample(cyclicBarrier,5000);
+        RunnableTaskExample runnableTask6=new RunnableTaskExample(cyclicBarrier,6000);
+
+        // Create and start 3 more threads
+        new Thread(runnableTask4,"Thread-4").start();
+        new Thread(runnableTask5,"Thread-5").start();
+        new Thread(runnableTask6,"Thread-6").start();
+
+
+    }
+}
+

src/main/java/tr/salkan/code/java/threadExecutor/example/threads/cyclicBarrier/RunnableTaskExample.java

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+package tr.salkan.code.java.threadExecutor.example.threads.cyclicBarrier;
+
+import java.util.concurrent.BrokenBarrierException;
+import java.util.concurrent.CyclicBarrier;
+
+public class RunnableTaskExample implements Runnable{
+
+    CyclicBarrier cyclicBarrier;
+    long sleepTime;
+
+    RunnableTaskExample(CyclicBarrier cyclicBarrier,long sleepTime){
+        this.cyclicBarrier=cyclicBarrier;
+        this.sleepTime=sleepTime;
+    }
+
+    @Override
+    public void run() {
+
+        try {
+            Thread.sleep(sleepTime);
+            System.out.println(Thread.currentThread().getName() +
+                    " is waiting for "+(cyclicBarrier.getParties()-cyclicBarrier.getNumberWaiting()-1)+
+                    " other threads to reach common barrier point");
+
+            cyclicBarrier.await();
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        } catch (BrokenBarrierException e) {
+            e.printStackTrace();
+        }
+
+        System.out.println("As "+cyclicBarrier.getParties()+ " threads have reached common barrier point "
+                + Thread.currentThread().getName() +
+                " has been released");
+    }
+
+}