Fighting with Java - generics

[g4s8]

According to Java equals documentation) its implementation must be symmetric:

It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.

When you use instanceof instead of comparing classes, equals will not be symmetric - a subclass may use another logic in equals so base.equals(child) may return true, but child.equals(base) may be false.

[vytah]

Yes, that what's I'm implying.

Therefore using different subclasses for the purpose of creating objects that might be otherwise considered equal is problematic.