Comparing Class Types in Java

Question

I want to compare the class type in Java.

I thought I could do this:

class MyObject_1 {} class MyObject_2 extends MyObject_1 {}  public boolean function(MyObject_1 obj) {    if(obj.getClass() == MyObject_2.class) System.out.println("true"); } 

I wanted to compare in case if the obj passed into the function was extended from MyObject_1 or not. But this doesn't work. It seems like the getClass() method and the .class gives different type of information.

How can I compare two class type, without having to create another dummy object just to compare the class type?

Answer 1

Try this:

MyObject obj = new MyObject(); if(obj instanceof MyObject){System.out.println("true");} //true 

Because of inheritance this is valid for interfaces, too:

class Animal {} class Dog extends Animal {}      Dog obj = new Dog(); Animal animal = new Dog(); if(obj instanceof Animal){System.out.println("true");} //true if(animal instanceof Animal){System.out.println("true");} //true if(animal instanceof Dog){System.out.println("true");} //true 

For further reading on instanceof: http://mindprod.com/jgloss/instanceof.html

Answer 2

If you don't want to or can't use instanceof, then compare with equals:

 if(obj.getClass().equals(MyObject.class)) System.out.println("true"); 

BTW - it's strange because the two Class instances in your statement really should be the same, at least in your example code. They may be different if:

• the classes have the same short name but are defined in different packages
• the classes have the same full name but are loaded by different classloaders.