Thread Class

The Thread class contains the constructors for creating threads for tasks and the methods for controlling threads.

Picture below shows the Thread class.As you may see here this class provides serveal useful methods manipulating the thread.

Thread creation by extending the Thread class

We create a class that extends the java.lang.Thread class. This class overrides the run() method available in the Thread class. A thread begins its life inside run() method. We create an object of our new class and call start() method to start the execution of a thread. Start() invokes the run() method on the Thread object.

Code below shows how to define a class extends Thread class to achive multithreading.

  // Java code for thread creation by extending
// the Thread class
  static class MultithreadingDemo extends Thread {

    public void run() {
      try {
        // Displaying the thread that is running
        System.out.println("Thread " +
            Thread.currentThread().getId() +
            " is running");

      } catch (Exception e) {
        // Throwing an exception
        System.out.println("Exception is caught");
      }
    }
  }

Then create two threads:

Thread threadOne = new MultithreadingDemo();
Thread threadTwo = new MultithreadingDemo();

threadOne.start();
threadTwo.start();

output:

Thread 11 is running
Thread 12 is running

yield() method to temporarily release time for other threads

package com.yieldMethodDemo;

public class YieldMethodDemo {

  public static void main(String[] args) {
    BuildThread buildThread = new BuildThread();
    DestroyThread destroyThread = new DestroyThread();
    buildThread.start();
    destroyThread.start();

  }

  static class BuildThread extends Thread {

    public void run() {
      for (int i = 0; i < 50; i++) {
        System.out.println("Build");
        if (i % 2 == 0) {
          Thread.yield();
        }

      }
    }
  }

  static class DestroyThread extends Thread {

    public void run() {
      for (int i = 0; i < 50; i++) {
        System.out.println("Destory");
      }
    }
  }
}

join() method demo

In CountingOne class’s run() method once i==5 then the countingOne thread will stop to wait the countingTwo thread to finish executing.

package com.ThreadJoinMethodDemo;

public class ThreadJoinMethodDemo {

  public static void main(String[] args) {
    CountingOne countingOne = new CountingOne();
    countingOne.start();
  }

  static class CountingOne extends Thread {

    public void run() {
      CountingTwo countingTwo = new CountingTwo();
      countingTwo.start();

      try {
        for (int i = 0; i < 10; i++) {
          if (i == 5) {
            countingTwo.join();
          }
          System.out.println(i);
        }
      } catch (InterruptedException e) {
        System.out.println(e);
      }
    }
  }

  static class CountingTwo extends Thread {

    public void run() {
      for (int i = 10; i < 20; i++) {
        System.out.println(i);
      }
    }
  }

}

output:

0
1
2
3
4
10
11
12
13
14
15
16
17
18
19
5
6
7
8
9