Introduction

• The yield() method in Java is used to temporarily pause the currently executing thread and give a chance for other threads of the same or higher priority to execute.
• When a thread calls Thread.yield(), it goes back to the Runnable state, so that the thread scheduler can decide which thread to run next.
• Real-World Examples where yield() is used:
  • CPU-intensive tasks: When a long-running thread gives other threads a chance to execute.
  • Background tasks: Low-priority tasks can yield CPU to higher-priority tasks when needed.
  • Multithreaded games: To let multiple game entities (like players or enemies) get execution time fairly.
• Java has provided the below yield() method in the Thread class:
  1. public static native void yield()
     • This is a native method, meaning its implementation is provided in another language (like C/C++) inside the JVM.
     • It is a static method, so it should be called as Thread.yield().
     • It does not guarantee that the current thread will stop; the decision depends on the thread scheduler.
• Program:

  class MyThread extends Thread
  {
      @Override
      public void run()
      {
          // Child thread prints numbers from 1 to 5
          for (int i = 1; i <= 5; i++)
          {
              System.out.println(getName() + " is running: " + i);
          }
      }
  }
  
  public class YieldDemo
  {
      public static void main(String[] args)
      {
          System.out.println("Main thread started execution.");
  
          // Main thread creates another thread (child thread)
          MyThread t1 = new MyThread();
          t1.setName("Child-Thread");
          t1.start();
  
          // Yielding once in the main method
          // 👉 Here the MAIN THREAD gives a chance (hint) to other threads of equal priority (Child-Thread)
          // If scheduler accepts the hint, Child-Thread will run first.
          Thread.yield();
  
          // Main thread continues its execution (printing 1 to 5)
          for (int i = 1; i <= 5; i++)
          {
              System.out.println("Main thread is running: " + i);
          }
  
          System.out.println("Main thread finished execution.");
      }
  }

  Output (If hint is accepted and child thread runs first):

  Main thread started execution.
  Child-Thread is running: 1
  Child-Thread is running: 2
  Child-Thread is running: 3
  Child-Thread is running: 4
  Child-Thread is running: 5
  Main thread is running: 1
  Main thread is running: 2
  Main thread is running: 3
  Main thread is running: 4
  Main thread is running: 5
  Main thread finished execution.

  Output (if hint is ignored and main thread continues):

  Main thread started execution.
  Main thread is running: 1
  Main thread is running: 2
  Main thread is running: 3
  Main thread is running: 4
  Main thread is running: 5
  Main thread finished execution.
  Child-Thread is running: 1
  Child-Thread is running: 2
  Child-Thread is running: 3
  Child-Thread is running: 4
  Child-Thread is running: 5

  Note: The yield() method is just a hint to the thread scheduler. It does not guarantee that the current thread will pause immediately or that another thread will run next. Behavior depends on the JVM and operating system.

• Important Key Points about yield() method:
  • yield() is a static method of the Thread class.
  • It is used to pause the current thread temporarily and give a chance to other threads of equal priority to execute.
  • The call to yield() is only a hint to the thread scheduler; it is not guaranteed that the current thread will stop executing.
  • If no other thread of equal priority is waiting, the same thread may continue its execution.
  • It does not release any locks (monitors) held by the thread.
  • The thread moves from Running state back to Runnable state after calling yield().
  • yield() is declared as native, meaning its actual implementation is provided in another language (like C/C++) inside the JVM.
  • The behavior of yield() is platform-dependent and may vary across operating systems and JVM implementations.