Comparing Class Types in Java

java types compare
Carven picture Carven · May 27, 2011 · Viewed 169k times · Source

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

Thor picture Thor · May 27, 2011

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

Related questions

java : convert float to String and String to float

How could I convert from float to string or string to float? In my case I need to make the assertion between 2 values string (value that I have got from table) and float value that I have calculated. String valueFromTable = "25"; …

Read More
Converting stream of int's to char's in java

This has probably been answered else where but how do you get the character value of an int value? Specifically I'm reading a from a tcp stream and the readers .read() method returns an int. How do I get a …

Read More
How do you know a variable type in java?

Let's say I declare a variable: String a = "test"; And I want to know what type it is, i.e., the output should be java.lang.String How do I do this?

Read More