Let us say we have a method which accepts two arguments o1 and o2 of type Object and returns a boolean value. I want this method to return true only when the arguments are instances of the same class, e.g.:

foo(new Integer(4),new Integer(5));

Should return true, however:

foo(new SomeClass(), new SubtypeSomeClass());

should return false and also:

foo(new Integer(3),"zoo");

should return false.

I believe one way is to compare the fully qualified class names:

public boolean foo(Object o1, Object o2){
 Class<? extends Object> c1 = o1.getClass();
 Class<? extends Object> c2 = o2.getClass();
 if(c1.getName().equals(c2.getName()){ return true;}
 return false;  
}

An alternative conditional statement would be :

if (c1.isAssignableFrom(c2) && c2.isAssignableFrom(c1)){ return true; }

The latter alternative is rather slow. Are there other alternatives to this problem?