How to Compare null?

Question

How do we compare null values ? For example, I am trying to compare null by

class_name == "null"

But the code doesn't checks if the class is null. What's wrong ?

Use `class_name == null` or improve your question if I didn't get the meaning. — fabian, Dec 22 '13 at 15:41

Maroun · Accepted Answer · 2013-12-22T16:26:58.757

6

You are comparing it to the reference of the String "null".

Remove the double quotes so you get the special null type (JLS).

You want:

class_name == null
              ↑

edited Dec 22 '13 at 16:26

answered Dec 22 '13 at 15:41

Maroun

can we use === instead of == ?? – user3127386 Dec 22 '13 at 15:45
No. Java != JavaScript. – Maroun Dec 22 '13 at 15:45
1

Please, don't give even a *hint* of the notion that one can *compare strings* with `==` :) – Marko Topolnik Dec 22 '13 at 16:25

score 1 · Answer 2 · edited May 22 '14 at 14:45

1

class_name == null because in your way you compare it to string not to null

edited May 22 '14 at 14:45

BenMorel

answered Dec 22 '13 at 15:42

Tareq Salah

2

is null an object or a data type, in Java ? – user3127386 Dec 22 '13 at 15:51
I'm sorry null is not an object in java (It is object in JavaScript) null is special type in java if you want more information about it in java you can look at this question http://stackoverflow.com/questions/2707322/what-is-null-in-java – Tareq Salah Dec 22 '13 at 15:53

score 0 · Answer 3 · edited Feb 13 '14 at 18:38

0

if(class_name == null)
    // do something;

edited Feb 13 '14 at 18:38

gunr2171

answered Dec 22 '13 at 15:42

3 Answers3