Synchronized with Another object

[luke brown]

in the below code snippet taken from http://docs.oracle.com/javase/tutorial/essential/concurrency/locksync.html

public class MsLunch {
    private long c1 = 0;
    private long c2 = 0;
    private Object lock1 = new Object();
   // private Object lock2 = new Object();
private Dummy lock2 = new Dummy();
    public void inc1() {
        synchronized(lock1) {
            c1++;
        }
    }

    public void inc2() {
        synchronized(lock2) {
            c2++;
        }
    }
}

Is it neccesary that the synchronized block member fields and variables must be held by the object used to lock it . i mean is it mandatory that c1 is a member of Dummy class or its parent class(Object class) instance ?

Regards
Luke

[Omkar Shetkar]

I think, if methods in a particular class are interdependent for state of the object, then it is good to use this/any single object as lock.
If two methods are not dependent (do not get affected by each others operations on the state of the object) then it is not harm to use different locks for the methods. This case is explained in your code.

Here, there is no reason that class used for lock should contain the state variables of synchronized block.