What is THREAD in JAVA ?

THREADS IN JAVA

Creating threads by constructor

class mythread implements Runnable //creates second thread

{  

     Thread t;

     int i;

     mythread()

     {

         t=new Thread(this,"mythread"); //creates new second thread

          t.start(); //start the thread       

     }    

     public void run()

     {                   

             for(i=0;i<5;i++)

             {

                 System.out.println("child thread " + i);                

             }                  

     }

}

public class Thread2 {     public static void main(String[] args)    {        new mythread();  //create new second thread          }}

EXAMPLE

class mythread implements Runnable

{

 int i ;

 public void run()

 {

   for(i=0;i<5;i++)

   {

     System.out.println("Child thread :" + i);

   }

 }

}

class createthread

{

 public static void main(String[ ] args)

 {

   mythread m1=new mythread();

   Thread th=new Thread(m1,"mythread");

  th.start();

 }

}

sleep() :-

makes currently executing thread to sleep for milliseconds.

Syntax:-

void sleep(long milliseconds);

 class mythread implements Runnable
{ 
     Thread t;     int i;     mythread()     {         t=new Thread(this,"mythread"); //creates new second thread                 t.start(); //start the thread      
     } }

public void run()     {         try         {          
             for(i=0;i<5;i++)             {                 System.out.println("child thread " + “hello world”);                 Thread.sleep(1000);             }         }         catch(Exception e)         {          
         }      
         System.out.println("Exitng child thread");     }  
  
}

public class Thread2 {

   

    public static void main(String[] args)

    {

        new mythread();  //create new second thread

        int i;

        try

         {            

             for(i=0;i<5;i++)

             {

                 System.out.println("Main thread " + i);

                 Thread.sleep(3000);

             }

         }

         catch(Exception e)

         {

            

         }

        

         System.out.println("Exitng Main thread");       

       

    }

}

—isAlive() :-

—Returns the value true or false depending on thread is terminated or not.

—

—getname():-

—Returns the name of the thread specified.

—

—currentThread() :-

—When a program is started thread is created automatically that is main thread and the main thread can be accessed using the current thread method of the main class.

—

class mythread implements Runnable //creates second thread{         Thread t;     int i;     mythread()     {         t=new Thread(this,"mythread"); //creates new second thread         System.out.println("  Child thread  :  " + t.getName() );System.out.println("Is Thread Alive ? " + t.isAlive());       
         t.start(); //start the threadSystem.out.println("Is Thread Alive ? " + t.isAlive());
              }  
     public void run()     {                 
             for(i=0;i<5;i++)             {                 System.out.println("child thread " + i);         
             }               
     }   
}

public class methods {

    public static void main(String[] args)

    {

       mythread m1= new mythread(); 

        System.out.println("The main thread is :" + Thread.currentThread().getName());

    }

}

Thread priorities

—

—Threads can be assigned priorities.

 —Thread priorities are used by operating system to find out which runnable thread is to be given C.P.U time.— — Priority is given from range 1-10.—  The threads with high priority number will be given preference over threads with lower priority for execution.

Pre-defined priorities

—MIN_PRIORITY =1

NORM_PRIORITY =5

MAX_PRIORITY =10

When thread is created default priority 5 is assigned to the thread.

Methods to get and set priority

—int getPriority();

setPriority(int priority_number);

class thread1 implements Runnable{  int i; public void run(){    for(i=0;i<5;i++)    {        System.out.println("child-1 " + i);     
    }}}

class thread2 implements Runnable{  int i; public void run(){    for(i=0;i<5;i++)    {        System.out.println("child-2 " + "hello world");     }}}

class prioritythread{ public static void main(String[ ] args) {    thread1 m1=new thread1();    thread2 m2=new thread2();Thread t=new Thread(m1,"thread1");Thread t1=new Thread(m2,"thread2"); t.setPriority(Thread.NORM_PRIORITY - 2);t1.setPriority(Thread.NORM_PRIORITY + 2);t.start(); t1.start();
}}

THREAD-JOIN 

—It may be required to wait for a particular thread to complete its task before

other process.—

—When join method of thread class is called on thread object , the control waits

for the thread to complete its task and becomes a dead thread.

class thread1 implements Runnable{  int i;
public void run(){   for(i=0;i<5;i++)    {        System.out.println("child-1 " + i); 
    }
   }
}

class jointhread{ public static void main(String[ ] args) { int i;    thread1 m1=new thread1();    thread2 m2=new thread2();    Thread t=new Thread(m1,"thread1");     t.start();try{t.join();for(i=0;i<5;i++){ System.out.println("hello world"); }}catch(Exception e){}}

}