Accessing Object using mutliple threads

Question

I created a class that creates 2 threads and both thread calls a method ( not synch..). In the method i create a new object.
Here is the code for it.
class ggh{
    public void m1(){
        ss s1= new ss();      // Simple class having 2 fields(int and string) and their getter setters
        System.out.println("S1 for thread #" + Thread.currentThread().getName() + "  ==> " + s1.toString()  );
        if(Thread.currentThread().getName().equals("Thread-0"))  // thread #1
            try {
                Thread.sleep(1000);      // -------------> 1
            s1.setA(2);                           // --------------> 2
            System.out.println("Settin s1 = null " + Thread.currentThread().getName());
                s1 = null;                         //  ---------------> 3
            } catch (InterruptedException ex) {
                ex.printStackTrace();
        System.out.println("s1 a==>" + s1.getA() + "::" + Thread.currentThread().getName() + " :: " + s1.toString());         //----------------> 4
    public static void main(String[] args) {
        final ggh g1 = new ggh();
        Thread t1 = new Thread(){
            public void run(){
                g1.m1();
        Thread t2 = new Thread(){
           public void run(){
                    g1.m1();
        t1.start();
        t2.start();
}when i execute this code, my output is totally unpredictable. Here are some of the outputs i got.
************** 1 The code creates the same object for both threads
S1 for thread #Thread-0 ==> vom.cdd.ss@defa1a
S1 for thread #Thread-1 ==> vom.cdd.ss@defa1a
s1 a==>1::Thread-1 :: vom.cdd.ss@defa1a
Settin s1 = null Thread-0
java.lang.NullPointerException
     at vom.cdd.ggh.m1(ggh.java:39)
     at vom.cdd.ggh$1.run(ggh.java:46)
************** 2 objects are different now.
S1 for thread #Thread-0 ==> vom.cdd.ss@f5da06
S1 for thread #Thread-1 ==> vom.cdd.ss@defa1a
s1 a==>1::Thread-1 :: vom.cdd.ss@defa1a
Settin s1 = null Thread-0
java.lang.NullPointerException
     at vom.cdd.ggh.m1(ggh.java:39)
     at vom.cdd.ggh$1.run(ggh.java:46)
************* 3 [Here nullpointer exception occurs before the null message is printed[/b]
S1 for thread #Thread-0 ==> vom.cdd.ss@defa1a
S1 for thread #Thread-1 ==> vom.cdd.ss@defa1a
s1 a==>1::Thread-1 :: vom.cdd.ss@defa1a
java.lang.NullPointerException
     at vom.cdd.ggh.m1(ggh.java:39)
     at vom.cdd.ggh$1.run(ggh.java:46)
Settin s1 = null Thread-0
So my question here is :
when such kind of unsynch. access occurs for some method. then does there exists a different object [b]( a new memory is allocated ) for each thread
or does there exist only one object and each thread has a different reference to it, and the thread can manipulate its properties.
Or does there exist a different explanation for this kind of behaviour??
One more thing, i dont wnat the method/a block of code to be synchronized.
I also have another doubt but willl post it after this one get's cleared.
Thanks in advance.
Regards
Akshat Jain

Answer 1

2 objects are different nowThey are not different at all. Address can differ at
each invocation.What do u mean that they are not different at all.
if they have different object's then obviously their address are different and henc the objects too.
am i getting this wrong??