How to identify object types in java

Question

Possible Duplicate:
How to determine an object's class (in Java)?
Java determine which class an object is

I have following sample incomplete method to compare the object type of a given object

public void test(Object value) {

        if (value.getClass() == Integer) {
            System.out.println("This is an Integer");
        }else if(value.getClass() == String){
            System.out.println("This is a String");
        }else if(value.getClass() == Float){
            System.out.println("This is a Float");
        }

}

The method can be called as:

test("Test");
test(12);
test(10.5f);

this method is not actually working, please help me to make it work

Duplicates : http://stackoverflow.com/q/541749/1140748 ; http://stackoverflow.com/q/6149677/1140748 — alain.janinm, May 10 '12 at 10:34

score 78 · Accepted Answer · answered May 10 '12 at 09:51

You forgot the .class:

if (value.getClass() == Integer.class) {
    System.out.println("This is an Integer");
} 
else if (value.getClass() == String.class) {
    System.out.println("This is a String");
}
else if (value.getClass() == Float.class) {
    System.out.println("This is a Float");
}

Note that this kind of code is usually the sign of a poor OO design.

Also note that comparing the class of an object with a class and using instanceof is not the same thing. For example:

"foo".getClass() == Object.class

is false, whereas

"foo" instanceof Object

is true.

Whether one or the other must be used depends on your requirements.

This is so painful. Currently we have to [implement Pattern Matching ourselves](https://kerflyn.wordpress.com/2012/05/09/towards-pattern-matching-in-java/) in every project. [Proposal to add to language.](http://openjdk.java.net/jeps/305) — JMess, Aug 21 '18 at 19:48

score 30 · Answer 2 · edited Oct 08 '17 at 06:28

You can compare class tokens to each other, so you could use value.getClass() == Integer.class. However, the simpler and more canonical way is to use instanceof :

    if (value instanceof Integer) {
        System.out.println("This is an Integer");
    } else if(value instanceof String) {
        System.out.println("This is a String");
    } else if(value instanceof Float) {
        System.out.println("This is a Float");
    }

Notes:

the only difference between the two is that comparing class tokens detects exact matches only, while instanceof C matches for subclasses of C too. However, in this case all the classes listed are final, so they have no subclasses. Thus instanceof is probably fine here.
as JB Nizet stated, such checks are not OO design. You may be able to solve this problem in a more OO way, e.g.
```
System.out.println("This is a(n) " + value.getClass().getSimpleName());
```

@PéterTörök Sorry I am completely tired and I mixed up the "== syntax" with the "instanceof one". I'll remove my comments as they are irrelevant. — Guillaume Polet, May 10 '12 at 11:04

score 7 · Answer 3 · answered May 10 '12 at 09:51

You want instanceof:

if (value instanceof Integer)

This will be true even for subclasses, which is usually what you want, and it is also null-safe. If you really need the exact same class, you could do

if (value.getClass() == Integer.class)

or

if (Integer.class.equals(value.getClass())

score 4 · Answer 4 · answered May 10 '12 at 09:51

4

Use value instanceof YourClass

answered May 10 '12 at 09:51

Konstantin V. Salikhov

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How to identify object types in java

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