[FIXED] Is it possible to use the instanceof operator in a switch statement?

Issue

I have a question of using switch case for instanceof object:

For example: my problem can be reproduced in Java:

if(this instanceof A)
    doA();
else if(this instanceof B)
    doB();
else if(this instanceof C)
    doC():

How would it be implemented using switch...case?

Solution

This is a typical scenario where subtype polymorphism helps. Do the following

interface I {
  void do();
}

class A implements I { void do() { doA() } ... }
class B implements I { void do() { doB() } ... }
class C implements I { void do() { doC() } ... }

Then you can simply call do() on this.

If you are not free to change A, B, and C, you could apply the visitor pattern to achieve the same.

Answered By - jmg
Answer Checked By - Candace Johnson (JavaFixing Volunteer)