Thread Priorities

Every Java thread has a priority that helps the operating system determine the order in which threads are scheduled.

Java thread priorities are in the range between MIN_PRIORITY (a constant of 1) and MAX_PRIORITY (a constant of 10). By default, every thread is given priority NORM_PRIORITY (a constant of 5).

public final int getPriority(): The java.lang.Thread.getPriority() method returns the priority of the given thread.

public final void setPriority(int newPriority): The java.lang.Thread.setPriority() method updates or assign the priority of the thread to newPriority. The method throws IllegalArgumentException if the value newPriority goes out of the range, which is 1 (minimum) to 10 (maximum).

A thread can voluntarily release control and the highest priority thread that is ready to run is given the CPU. A thread can be preempted by a higher priority thread no matter what the lower priority thread is doing. Whenever a higher priority thread wants to run it does.

Thread priorities cannot guarantee the order in which threads execute and are very much platform dependent.

Ex:

import java.lang.*; 

public class ThreadPriorityExample1 extends Thread  

{ 

 public void run() 

{ 

System.out.println("Inside the run() method"); 

} 

public static void main(String argvs[]) 

{ 

Thread.currentThread().setPriority(7); 

System.out.println("Priority of the main thread is : " + Thread.currentThread().getPriority()); 

ThreadPriorityExample1 th1 = new ThreadPriorityExample1(); 

System.out.println("Priority of the thread th1 is : " + th1.getPriority()); 

} 

}