Multithreaded Programming

Java provides built-in support for multithreaded programming. A multithreaded program contains two or more parts that can run concurrently. Each part of such a program is called a thread. Each thread defines a separate path of execution.

Java's multithreading system is built upon the Thread class and Runnable interface. To create a new thread, your program will either extend Thread or implement the Runnable interface.

The Thread class defines several methods that help manage threads.

Method	Meaning
getName	Obtain a thread's name.
getPriority	Obtain a thread's priority.
isAlive	Determine if a thread is still running.
join	Wait for a thread to terminate.
run	Entry point for the thread.
sleep	Suspend a thread for a period of time.
start	Start a thread by calling its run method.

Thread declares several deprecated methods, including stop(). These methods have been deprecated because they are unsafe. Do not use these deprecated methods.

The following code shows a pair of counting threads.

 
public class Main {
  public static void main(String[] args) {
    Runnable r = new Runnable() {
      @Override
      public void run() {
        String name = Thread.currentThread().getName();
        int count = 0;
        while (count< Integer.MAX_VALUE)
          System.out.println(name + ": " + count++);
      }
    };
    Thread thdA = new Thread(r);
    Thread thdB = new Thread(r);
    thdA.start();
    thdB.start();
  }
}

The following code sets name to threads.

 
public class Main {
  public static void main(String[] args) {
    Runnable r = new Runnable() {
      @Override
      public void run() {
        String name = Thread.currentThread().getName();
        int count = 0;
        while (count<Integer.MAX_VALUE) {
          System.out.println(name + ": " + count++);
          try {
            Thread.sleep(100);
          } catch (InterruptedException ie) {
          }
        }
      }
    };
    Thread thdA = new Thread(r);
    thdA.setName("A");
    Thread thdB = new Thread(r);
    thdB.setName("B");
    thdA.start();
    thdB.start();
  }
}

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