如何摆脱ClassCastException

Question

假设我有2个完全不同的用户定义类A和B

A a = new A();

B b = new B();

. . .

. . .

a = (A) b; //I'm pretty sure this raises a ClassCastException, but how to deal with this issue?

Answer 1

You can't, unless B derives from A.
That's the point of a ClassCastException.

But since A and B are totally different, why would you want to convert them in the first place?

Answer 2

Testing before assign the variable.

In java:

if(a instanceof B)
    b = (B) a;

In C#:

if(a is B)
    b = (B) a;

But as someone mentioned if you do not derive the class a and b from c I cant see to much benefit of this assignment.