thread problem help!!

[gourav1]

class thr2
{
	public static void main(String args[])
	{
		A a = new A("first","hello1");
		A a1= new A("second","hello2");


		try{
			a.t.join();
			a1.t.join();
		}catch(Exception e)
		{

		}
	}
}

class A  implements Runnable
{
	Thread t;
	String str;
	B b = new B();

	A(String name,String str)
	{
		t=new Thread(this,name);
		t.setName(name);
		this.str=str;
		t.start();
	}

	public void run()
	{
		b.sum(str);
	}


}

class B
{
    synchronized void sum(String str)
	{
		System.out.print("[" + str);
		try
		{
			Thread.sleep(100);
		}catch(Exception e)
		{

		}

		System.out.println("]");
	}
}

when synchronized with sum() is used then output is same when it is not there. tell me y it is not working here?

[zeroliken]

post the whole error message from the compiler

[gourav1]

post the whole error message from the compiler

there is not any error! it is completely running. but when i use synchronised then output must be like this [hello1] [hello2] nut it is not coming like that. it is exactly same as when synchronised is not there. you can also check

[zeroliken]

Did you post your whole code? Are the classes in separate java files? wheres the public class?

[gourav1]

Are the classes in separate java files? wheres the public class?

no. it is one .java file. i have not made any class as public. is it neccessary to do that ??

[JamesCherrill]

What output do you get; [hello1[hello2]] ?
A synchronised method like yours is synchronised on the current object (instance of the class). Because you have two different instances of B each invocation of sum is synchronised on a different object, so the synchronisation has no effect. If you synchronise them both on the same object you will get the expected output.

[gourav1]

What output do you get; [hello1[hello2]] ?
A synchronised method like yours is synchronised on the current object (instance of the class). Because you have two different instances of B each invocation of sum is synchronised on a different object, so the synchronisation has no effect. If you synchronise them both on the same object you will get the expected output.

no. there is only one object of B (b here). where are two according to u ?

[JamesCherrill]

No, you have two instances of A, each of which creates its own instance of B, so that's two B's.

If you had
static B b = new B();
then there would only be one b.

[zeroliken]

t.setName(name);

where can setName method be found?

[gourav1]

No, you have two instances of A, each of which creates its own instance of B, so that's two B's.

If you had
static B b = new B();
then there would only be one b.

ohh ya ya! that's right! hey! how do u answer every question so easily ? it's damn impressive!

[JamesCherrill]

Been there before, usually. Pls mark this "solved" if you're happy.

[gourav1]

Been there before, usually. Pls mark this "solved" if you're happy.

please one more question! will u exactly tell me use of wait() and notify()? i have read many many examples but i m not getting it. please help if u can. will be thankful to u

[JamesCherrill]

sorry man, I'm not going to try to write a tutorial here, even if I had the time. There are loads on the web already, most of them better than I could do anyway. Like these:
http://www.java-samples.com/showtutorial.php?tutorialid=306
http://www.avajava.com/tutorials/lessons/how-do-i-use-the-wait-and-notify-methods.html
Read them carefully then, if you have specific questions, start a new thread for it.
OK?
J

[gourav1]

sorry man, I'm not going to try to write a tutorial here, even if I had the time. There are loads on the web already, most of them better than I could do anyway. Like these:
http://www.java-samples.com/showtutorial.php?tutorialid=306
http://www.avajava.com/tutorials/lessons/how-do-i-use-the-wait-and-notify-methods.html
Read them carefully then, if you have specific questions, start a new thread for it.
OK?
J

ok ok! i will start a new thread as u said if i have for wait(). thanks for this thread. this is solved by you.

[zeroliken]

I was checking other threads then came back here only to find that JamesCherrill found the solution so simply:-O
Took me a while to see that...Just goes to show the difference in experience

@OP
sorry wasn't much help:$