run() method not executing using start()

Question

i want to just use join() and isAlive function. I created 4 threads and initialized them in constructor. I started threads by using start method. It should call run() but the run method is not executing. Am i doing something wrong. Please tell me. Thank You in advance.

  class MultiThreads implements Runnable {

    String name;
    Thread t;

    MultiThreads(String tname) {
        name=tname;
        t=new Thread(this.name);
        System.out.println("Thread name: " + t);
        t.start();              //executing run()
    }

    public void run(){

       try{
         for(int i=1;i<11;i++){
            System.out.println("Thread-"+name+ ": " + i);
            t.sleep(500);           
            }
       }catch(Exception ie){
           System.out.println("An error has occurred");
        }
    }
 }

public class JoinAlive {

    public static void main(String args[]) {

        //Creating New Threads by calling constructor.

        MultiThreads t1=new MultiThreads("One");``
        MultiThreads t2=new MultiThreads("Two");
        MultiThreads t3=new MultiThreads("Three");
        MultiThreads t4=new MultiThreads("Four");

        System.out.println();

        System.out.println("Thread-One active: " + t1.t.isAlive());
        System.out.println("Thread-Two active: " + t2.t.isAlive());
        System.out.println("Thread-Three active: " + t3.t.isAlive());
        System.out.println("Thread-Four active: " + t4.t.isAlive());

       try{
           System.out.println();
           System.out.println(" Waiting for One");
           t1.t.join();
           System.out.println(" Waiting for Two");
           t2.t.join();
         }catch(InterruptedException ie){
             System.out.println("An error occurred");
          }

          System.out.println();

          System.out.println("Thread-One active: " + t1.t.isAlive());
          System.out.println("Thread-Two active: " + t2.t.isAlive());
          System.out.println("Thread-Three active: " + t3.t.isAlive());
          System.out.println("Thread-Four active: " + t4.t.isAlive());
     }
 }

Answer 1

Use this edited Code `class MultiThreads implements Runnable {

String name;
Thread t;

MultiThreads(String tname) {
    name=tname;
    t=new Thread(this.name);
    System.out.println("Thread name: " + t);
    t.start();              //executing run()
}

public void run(){

   try{
     for(int i=1;i<11;i++){
        System.out.println("Thread-"+name+ ": " + i);
        t.sleep(500);           
        }
   }catch(Exception ie){
       System.out.println("An error has occurred");
    }
}

}

public class JoinAlive {

public static void main(String args[]) {

    //Creating New Threads by calling constructor.

    Thread t1=new Thread(new MultiThreads("One"));
    Thread t2=new Thread(new MultiThreads("Two"));
    Thread t3=new Thread(new MultiThreads("Three"));
    Thread t4=new Thread(new MultiThreads("Four"));

    System.out.println();

    System.out.println("Thread-One active: " + t1.isAlive());
    System.out.println("Thread-Two active: " + t2.isAlive());
    System.out.println("Thread-Three active: " + t3.isAlive());
    System.out.println("Thread-Four active: " + t4.isAlive());

   try{
       System.out.println();
       System.out.println(" Waiting for One");
       t1.join();
       System.out.println(" Waiting for Two");
       t2.join();
     }catch(InterruptedException ie){
         System.out.println("An error occurred");
      }

      System.out.println();

      System.out.println("Thread-One active: " + t1.isAlive());
      System.out.println("Thread-Two active: " + t2.isAlive());
      System.out.println("Thread-Three active: " + t3.isAlive());
      System.out.println("Thread-Four active: " + t4.isAlive());
 }

} `

Answer 2

The creation of the Thread object in your code is a Thread without a target.

You are using this:

t=new Thread(this.name);

You should initialize your thread with this:

t=new Thread(this, this.name);

It'll link the run method of your Runnable to the start method of your Thread.

---

Hope this helps!

Answer 3

t=new Thread(this.name); is the problem.
You give a name to the thread but you don't provide the associated target Runnable instance.

Just use this constructor :

public Thread(Runnable target, String name) 

in this way :

t=new Thread(this,this.name);