What are the different ways of creating thread in Java?

Question

import java.util.ArrayList;
import java.util.List;

public class ThreadB extends Thread {
    private static List<String> list1   = new ArrayList<String>();
    private static List<String> list2   = new ArrayList<String>();
    private static final Object mutex   = new Object();

    public void run() {
        try {
            sleep(2000l);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        synchronized (mutex) {
            list1.add("Hello");
            System.out.println("Added for 1   " + list1.size());
            list2.add("Added for 2");
            System.out.println("Added for 2   " + list2.size());
            mutex.notify();
        }
    }

    public static void main(String[] args) {
        ThreadB a1 = new ThreadB();
        ThreadB a2 = new ThreadB();
        a1.start();
        a2.start();
        new ThreadB().m1();    
    }

    private void m1() {         
        synchronized (list1) {
            System.out.println(list1.size());
            System.out.println(list2.size());
            try {
                list1.add("hello");
                System.out.println("m1  :::   " + list1.size());
                sleep(5000l);
                System.out.println("Oh mY God");
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }
    }
}

Output is

0
0
m1  :::   1
Added for 1   2
Added for 2   1
Added for 1   3
Added for 2   2
Oh mY God

After locking list1, how other threads are going to access that list?

Answer 1

There are two ways of creating thread.

(1) Implementing Runnable: The Runnable interface defines a single method, run, meant to contain the code executed in the thread. The Runnable object is passed to the Thread constructor, as in the HelloRunnable example

    public class HelloRunnable implements Runnable { 
         public void run() { 
              System.out.println("Hello from a thread!"); 
       } 

   public static void main(String args[]) { 
       (new Thread(new HelloRunnable())).start(); 
        } 
  }

(2) Subclass Thread. The Thread class itself implements Runnable interface, though it runs method does nothing. An application can subclass Thread, and provides its own implementation of run, as in the HelloThread example:

     public class HelloThread extends Thread { 
          public void run() { 
          System.out.println("Hello from a thread!"); 
                 } 
    public static void main(String args[]) 
    { 
           (new HelloThread()).start(); 
        } 
   }