Question

I have a simple problem:

Class A{

    B b;

    public void doSth{ 
         //This method should execute only once
         b.modify(); //calls doSth() again...
    }
}

As the program runs, an instance of A is passed to B, and B calls doSth (as a callback for instance). b.modify makes B to call A.doSth() again, which will infinite sequence of calls. What I want to achieve is this: I want to execute doSth() once, modify B, then upon next execution somehow stop the chain of inifinite calls and do not execute b.modify.

Any suggestions greatly appreciated.

Answer 1

Add a state flag to your class:

Class A {

    B b;
    private volatile boolean called;

    public synchronized void doSth { 
         if (called) return;
         called = true;
         b.modify();
    }
}

Use volatile if multiple threads are in play.