Regarding synchronization

[Tusshar Fasate]

Suppose,I hava 10 methods in my class say method1(),method2(),.....method10()..

And I am calling method10() in method9(),method9() in method8()..till method1()...

If I marked method1() as synchronized Is there any need to mark other 9 methods as synchornized?

Please reply to this my confusion.

[Amit Vinod Dali]

When a thread invokes a synchronized method, it automatically acquires the lock for that method's object and releases it when the method returns. The lock release occurs even if the return was caused by an uncaught exception.
So there is not need mark other 9 methods as synchornized(unless it is required).

[Doug Braidwood]

You can call non-synchronized methods from synchronized ones but you should probably think carefully before doing so.

Whilst you are in one of the synchronized methods of an object, any methods which are not synchronized can still be accessed by other threads.

For example this code will return Two times 2 is 6 even though the method doubler is synchronized.
However if you also make setX synchronized it will work correctly.

  public class SyncTest implements Runnable{
	
	private int x;
	
	public void setX(int aNumber){
		x = aNumber;
	}
	
	public synchronized void doubler(int aNumber){
		setX(aNumber);
		String output = "Two times " + aNumber + " is ";
		try{
			Thread.sleep(1000);
		}
		catch (InterruptedException e){
		}
		output += (x*2);
		System.out.println(output);	
	}
	public void run(){
			doubler(2);
		}

	public static void main(String[] args){
		SyncTest s = new SyncTest();
		Thread t = new Thread(s);
		t.start();
		try{
			Thread.sleep(100);
		}
		catch (InterruptedException e){
		}
		s.setX(3);
	}
}