Introduction to Programming

Preferring polymorphism over the instanceof operator

The instance of operator is very helpful. We have used it several times in this book. But, there are situations that may require us to revisit the decision to use it.

Every time you think about using the instanceof operator, try to see if you can avoid it by using polymorphism.

To illustrate this tip, here is some code that can benefit from polymorphism instead of using the intanceof operator:

class ClassBase {}class ClassY extends ClassBase {  void method(){

    System.out.println("ClassY.method() is called");  }}class ClassZ extends ClassBase {  void method(){    System.out.println("ClassZ.method() is called");  }}class SomeClass{  public void doSomething(ClassBase object) {    if(object instanceof ...