Thread priority in java with example

Thread priority is useful to maintain threads in an order in java. When multiple threads are created and started, a 'Thread Scheduler' program will load all threads into JVM memory and executes them based on thread priority. This scheduler will allot more JVM time to those threads which are having higher priorities.

          The priority number of a thread will change from 1 to 10. The minimum priority (Thread.MIN_PRIORITY) of a thread is 1, and the maximum priority (Thread.MAX_PRIORITY) is 10. The normal priority of a thread (Thread.NORM_PRIORITY) is 5.

Example: Let us write a program to understand the thread priority. The thread with higher priority number will complete its execution first.

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package com.javatbrains.threads; class ThreadPriority extends Thread { int count = 0; public void run() { for (int i = 0; i < 10000; i++) count++;// count numbers up to 10000 // Display which thread has completed counting and its priority System.out.println("Completed Thread: " + Thread.currentThread().getName()); System.out.println("Its Priority: " + Thread.currentThread().getPriority()); } } public class Priority { public static void main(String[] args) { ThreadPriority prior = new ThreadPriority(); //Create two threads Thread t1 = new Thread(prior, "First"); Thread t2 = new Thread(prior, "Second"); //Set priorities for them t1.setPriority(Thread.MIN_PRIORITY); t2.setPriority(Thread.MAX_PRIORITY); //start first t1 and then t2 t1.start(); t2.start(); } } OutPut: Completed Thread: Second Its Priority: 10 Completed Thread: First Its Priority: 1

Daemon Thread:

          A daemon thread is a thread that executes continuously. Daemon threads are service providers for other threads or objects. It generally provides a background processing.

              •  To make a thread t as a daemon thread, we can use setDaemon() method as,

1	t.setDaemon(true);

              • To know if a thread is daemon or not, isDaemon() is useful.

1	boolean x = t2.isDaemon();

Animation Application Using Thread

          Let us see the use of the thread in animation application, where an object, an image or some text is moved from one place to another on the screen Here is an example program to see a moving banner using a thread. The logic is to extract the first character from a banner string and add it at the end of the string.

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package com.javatbrains.threads; import java.awt.Color; import java.awt.Font; import java.awt.Frame; import java.awt.Graphics; public class Banner extends Frame implements Runnable{ //This is the banner String String str = "JAVATBRAINS.BLOGSPOT.IN"; public Banner(){ setLayout(null); setBackground(Color.CYAN); setForeground(Color.RED); } public void paint(Graphics g){ //Set a font and display the banner string Font f = new Font("times new roman", Font.BOLD, 40); g.setFont(f); g.drawString(str, 10, 100); } @Override public void run() { for(;;){ //Move banner continuously repaint(); //Refresh the frame contents try{ Thread.sleep(1000); //Give a gap of each movement }catch(InterruptedException ie){ ie.printStackTrace(); } char ch = str.charAt(0); str = str.substring(1,str.length()); str = str+ch; //attach the first character at the end of str } } public static void main(String[] args) { Banner b = new Banner(); b.setSize(670, 150); b.setTitle("BLOGSPOT.COM"); b.setVisible(true); //create a thread and run it Thread t = new Thread(b); t.start(); } }

About GREEN and NATIVE threads:

Both the threads are mechanism support to multithread execution of Java program.

Green Thread:

          Green Threads are threads are scheduled by a JVM. Green is earlier JVM project code name. It is name of library which is provided VM-scheduled threads in Java-1.1. Green threads refers to a model in which the JVM itself creates, manages and context switches all java threads with in one operating system process. No operating system threads library is used. Green threads are in past, JVM's will work only with native threads since JDK 1.3.

Native Threads:

          Native threads are scheduled by an operating system. Native thread called so because they are belong to native platform. Native thread refers to a in which JVM creates and manages. Java thread using the operating system thread library – named lib thread on UnixWare – and each Java thread is mapped to one threads library thread.

Do you know?

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Thread priority in java with example