Question

So to make a long story short. A professor asked this question in class as a discussion starter. Besides the obvious

B = new SomeClass("B"); // But B can be null, can can be new SomeClass("A");
A = new SomeClass("A");
A==B

will guarantee no NPE when comparing, what are the reasons to use B==A instead of A==B?

Where A and B are of same type, and this is language independent. So you can assume A.equals(B) for Java, or equivalent syntax in C or C++ etc….

And no, this is not homework.

Answer 1

In Java, A == B and B == A always have the same semantics. In C# (which has operator overloading), there can be a difference if, say, B is an instance of a subclass of the class of A.

Note that A.equals(B) is not equivalent to A == B.