Java Multithreading Programming Tutorial with Examples

package org.o7planning.tutorial.thread.hellothread;

public class HelloMain {

   public static void main(String[] args) throws InterruptedException {

       int idx = 1;

       for (int i = 0; i < 2; i++) {

           System.out.println("Main thread running " + idx++);
           // Sleep 2101 miliseconds.
           Thread.sleep(2101);
       }

       HelloThread helloThread = new HelloThread();

       // Run thread
       helloThread.start();

       for (int i = 0; i < 3; i++) {
           System.out.println("Main thread running " + idx++);

           // Sleep 2101 miliseconds.
           Thread.sleep(2101);
       }

       System.out.println("==> Main thread stopped");
   }
}

package org.o7planning.tutorial.thread.hellothread;

public class HelloThread extends Thread {


   // Code of method run() will be executed when
   // thread call start()
   @Override
   public void run() {
       int index = 1;

       for (int i = 0; i < 10; i++) {
           System.out.println("  - HelloThread running " + index++);

           try {
               // Sleep 1030 miliseconds.
               Thread.sleep(1030);
           } catch (InterruptedException e) {
           }

       }
       System.out.println("  - ==> HelloThread stopped");
   }
}

package org.o7planning.tutorial.thread.runnable;

public class RunnableDemo implements Runnable {

   @Override
   public void run() {
       int idx = 1;
       for (int i = 0; i < 5; i++) {
           System.out.println("Hello from RunnableDemo " + idx++);

           // Sleep 2 second.
           try {
               Thread.sleep(2000);
           } catch (InterruptedException e) {
           }
       }
   }

}

package org.o7planning.tutorial.thread.runnable;

public class RunnableTest {

   public static void main(String[] args) throws InterruptedException {

       System.out.println("Main thread running..");

       // Create a thread from Runnable.
       Thread thread = new Thread(new RunnableDemo());

       thread.start();

       // Sleep 5 seconds.
       Thread.sleep(5000);
       System.out.println("Main thread stopped");
   }
}

Thread thread = new MyThread();

// marks this thread as a daemon thread
// This method is only called when the thread is not a start.
// In the case of start, it will be throws an exception.
thread.setDeamon(true);


// marks this thread as a none-daemon thread
// This method is only called when the thread is not a start.
// In the case of start, it will be throws an exception.
thread.setDeamon(false);

package org.o7planning.tutorial.thread.deamon;

public class NoneDeamonThread extends Thread {

   @Override
   public void run() {
       int i = 0;

       // Loop 10 times. This thread will end.
       while (i < 10) {
           System.out.println("  - Hello from None Deamon Thread " + i++);
           try {

               // Sleep 1 second
               Thread.sleep(1000);
           } catch (InterruptedException e) {
           }
       }

       // None deamon thread ending.
       System.out.println("\n==> None Deamon Thread ending\n");
   }
}

package org.o7planning.tutorial.thread.deamon;

class DeamonThread extends Thread {

   @Override
   public void run() {
       int count = 0;
     
       // Infinite loop
       while (true) {
           System.out.println("+ Hello from Deamon Thread " + count++);
           try {
               // Sleep 2 second
               sleep(2000);
           } catch (InterruptedException e) {
           }
       }
   }
}

package org.o7planning.tutorial.thread.deamon;

public class DaemonTest {

   public static void main(String[] args) {
       System.out.println("==> Main Thread running..\n");

       // Create thread
       Thread deamonThread = new DeamonThread();

       // Set deamon true
       deamonThread.setDaemon(true);
       deamonThread.start();

       // Create other thread
       new NoneDeamonThread().start();

       try {
           // Sleep 5 second
           Thread.sleep(5000);
       } catch (InterruptedException e) {
       }
     
       // Main Thread ending
       System.out.println("\n==> Main Thread ending\n");
   }

}

// Parent thread must wait until the end of this thread, before being continued.
// (This is equivalent to calling join(0))
public final void join() throws InterruptedException;

// Parent thread must wait 'millis' milliseconds to continue running.
// After call join(long).
// If the parameter millis = 0 means to wait until the end of this thread.
public final synchronized void join(long millis) throws InterruptedException;


// Parent thread must wait 'millis' milliseconds and 'nanos' nanoseconds to continue running.
// After call join(long,int).
// 1 second = 1000000 nanoseconds.
public final synchronized void join(long millis, int nanos) throws InterruptedException;

package org.o7planning.tutorial.thread.join;

public class JoinThread extends Thread {
  private String threadName;
  private int count;

  public JoinThread(String threadName, int count) {
      this.threadName = threadName;
      this.count = count;
  }

  @Override
  public void run() {

      for (int i = 1; i < count + 1; i++) {
          System.out.println("Hello from " + this.threadName + " " + i);
          try {
              Thread.sleep(2000);
          } catch (InterruptedException e) {
          }
      }
      System.out.println("\n==> Thread " + threadName + " end!\n");
  }
}

package org.o7planning.tutorial.thread.join;

public class JoinTest {

   public static void main(String[] args) throws InterruptedException {

       System.out.println("\n==> Main thread starting..\n");

       Thread joinThreadA = new JoinThread("A*", 2);
       Thread joinThreadB = new JoinThread("B*", 3);


       // None join Thread.
       Thread noJoinThreadC = new JoinThread("C", 5);

       joinThreadA.start();
       joinThreadB.start();
       noJoinThreadC.start();

       // Using join()
       joinThreadA.join();
       joinThreadB.join();


       // The following code will have to wait until 2
       // JoinThread A, B completed.
       System.out.println("Hello from main thread...");

       System.out.println("Thread A isLive? " + joinThreadA.isAlive());
       System.out.println("Thread B isLive? " + joinThreadB.isAlive());
       System.out.println("Thread C isLive? " + noJoinThreadC.isAlive());

       System.out.println("\n==> Main Thread end!\n");
   }
}

package org.o7planning.tutorial.thread.join;

public class JoinTest2 {

   public static void main(String[] args) throws InterruptedException {

       System.out.println("\n==> Main thread starting..\n");

       Thread joinThreadA = new JoinThread("A*", 5);

       joinThreadA.start();
       
       // Main thread must wait to 5000 miliseconds,
       // and then continue running. (Not necessarily joinThreadA finish)
       joinThreadA.join(5000);

       System.out.println("Main thread after 5000 milli second");
       System.out.println("Hello from main thread...");

       System.out.println("Thread A isLive? " + joinThreadA.isAlive());

       System.out.println("\n==> Main Thread end!\n");
   }

}

package org.o7planning.tutorial.thread.exception;

import java.util.Random;

public class ThreadExceptionDemo {

   public static class RunnableTest implements Runnable {

       @Override
       public void run() {
           System.out.println("Thread running ..");

           while (true) {
               Random r = new Random();

               // A random number from 0-99
               int i = r.nextInt(100);
               System.out.println("Next value " + i);

               try {
                   Thread.sleep(2000);
               } catch (InterruptedException e) {
               }

               if (i > 70) {
                    // Simulate an exception was not handled in the thread.
                   throw new RuntimeException("Have a problem...");
               }
           }
       }

   }

   public static void main(String[] args) {
       System.out.println("==> Main thread running...");

       Thread thread = new Thread(new RunnableTest());
       Thread.setDefaultUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {

           @Override
           public void uncaughtException(Thread t, Throwable e) {
               System.out.println("#Thread: " + t);
               System.out.println("#Thread exception message: " + e.getMessage());
           }
       });

       thread.start();
       System.out.println("==> Main thread end...");
   }

}

public static native void yield();

package org.o7planning.tutorial.thread.yield;

import java.util.Date;

public class YieldThreadExample {

	private static Date importantEndTime;
	private static Date unImportantEndTime;

	public static void main(String[] args) {
		importantEndTime = new Date();
		unImportantEndTime = new Date();

		System.out.println("Create thread 1");

		Thread importantThread = new ImportantThread();

		// Set the highest priority for this thread.
		importantThread.setPriority(Thread.MAX_PRIORITY);

		System.out.println("Create thread 2");

		Thread unImportantThread = new UnImportantThread();

		// Set the lowest priority for this thread.
		unImportantThread.setPriority(Thread.MIN_PRIORITY);

		// Start threads.
		unImportantThread.start();
		importantThread.start();

	}

	// A important job which requires high priority.
	static class ImportantThread extends Thread {

		@Override
		public void run() {
			for (int i = 0; i < 100000; i++) {
				System.out.println("\n Important work " + i);

				// Notifying the operating system,
				// this thread gives priority to other threads.
				Thread.yield();
			}

			// The end time of this thread.
			importantEndTime = new Date();
			printTime();
		}

	}

	static class UnImportantThread extends Thread {
		@Override
		public void run() {
			for (int i = 0; i < 100000; i++) {
				System.out.println("\n  -- UnImportant work " + i);
			}
			// The end time of this thread.
			unImportantEndTime = new Date();
			printTime();
		}
	}

	private static void printTime() {
		// Interval (Milliseconds)
		long interval = unImportantEndTime.getTime() - importantEndTime.getTime();

		System.out.println("UnImportant Thread - Important Thread = " //
				+ interval + " milliseconds");
	}

}