MultiThreading

Thread creation by implementing the Runnable Interface

• We create a new class which implements Runnable interface and override run() method.
• The code which we want to execute concurrently must be placed in run() method.
• Then we create a Thread object by passing object of above class as arg and call start() method on this thread object.

Interface Runnable

• The Runnable interface should be implemented by any class whose objects are intended to be executed by a thread.

• public abstract void run()
• When an object implementing interface Runnable is used to create a thread, starting the thread causes the object's run method to be called in that separately executing thread.

 class MyTask extends Thread
 {
    public void run()
    {
        for(int i=1;i<=200;i++)
 	        System.out.print(i+"- ");
    }
 }
 class YourTask implements Runnable
 {
    public void run()
    {
        for(int i=1;i<=200;i++)
	        System.out.print(i+"= ");
   }
 }
 class demo
 {
    public static void main(String args[])          
    {
        MyTask tsk1=new MyTask();	
        YourTask tsk2=new YourTask();	
        Thread trd=new Thread(tsk2);
        tsk1.start();
        trd.start();
    }
 }

Life cycle of a Thread

• NewBorn : A thread begins its life cycle when the new thread obj is created. It remains in this state until the start() method is called on it
• Runnable/Ready : After invocation of start() method on new thread, the thread becomes runnable.
• Running :A thread is in running state if the thread scheduler has selected it.
• Waiting/Blocked : A thread is in waiting state if it waits for another thread to perform a task. In this stage the thread is still alive.
• Terminated/Dead : A thread enter the terminated state when it complete its task.

Thread Priorities

• Every thread has a priority that helps the operating system determine the order in which threads are scheduled for execution.
• In java thread priority ranges between 1 to 10.
• MIN-PRIORITY (a constant of 1)
• MAX-PRIORITY (a constant of 10)
• By default every thread is given a NORM-PRIORITY(5).
• The main thread always have NORM-PRIORITY.
• Thread priority can be set / get by using methods
• void setPriority( int priority )
• int getPriority( )