Compare an object to null in Java

Question

I am trying to verify whether an object is null or not, using this syntax:

void renderSearch(Customer c) {
    System.out.println("search customer rendering>...");
    try {
        if (!c.equals(null)) {
            System.out.println("search customer  found...");
        } else {
            System.out.println("search customer not found...");
        }
    } catch (Exception e) {
        System.err.println("search customer rendering error: "
                + e.getMessage() + "-" + e.getClass());
    }
}

I get the following exception:

search customer rendering error: null
class java.lang.NullPointerException

I thought that I was considering this possibility with my if and else statement.

plus. if and else is not called a loop. its a condition

Midhat
– Midhat

2009-06-15 04:00:25 +00:00
Commented Jun 15, 2009 at 4:00 — Midhat
– Midhat, Commented Jun 15, 2009 at 4:00

Ola Ström · Accepted Answer · 2023-03-06 13:46:37Z

30

You're not comparing the objects themselves, you're comparing their references.

Try

c != null

in your if statement.

edited Mar 6, 2023 at 13:46

Ola Ström

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answered Jun 15, 2009 at 3:50

S.P

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Comments

Greg Leaver · Accepted Answer · 2009-06-15 03:53:44Z

13

!c.equals(null)

That line is calling the equals method on c, and if c is null then you'll get that error because you can't call any methods on null. Instead you should be using

c != null

answered Jun 15, 2009 at 3:53

Greg Leaver

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Comments

Alex Martelli · Accepted Answer · 2009-06-15 03:51:47Z

11

Use c == null, since you're comparing references, not objects.

answered Jun 15, 2009 at 3:51

Alex Martelli

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Comments

Midhat · Accepted Answer · 2009-06-15 03:52:48Z

8

Use c==null

The equals method (usually) expects an argument of type customer, and may be calling some methods on the object. If that object is null you will get the NullPointerException.

Also c might be null and c.equals call could be throwing the exception regardless of the object passed

answered Jun 15, 2009 at 3:52

Midhat

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Comments

Nrj · Accepted Answer · 2009-06-15 04:23:51Z

3

Most likely Object c is null in this case.

You might want to override the default implementation of equals for Customer in case you need to behave it differently.

Also make sure passed object is not null before invoking the functions on it.

answered Jun 15, 2009 at 4:23

Nrj

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Comments

José García · Accepted Answer · 2018-12-16 23:57:19Z

-3

The reality is that when c is null, you are trying to do null.equals so this generates an exception. The correct way to do that comparison is "null".equals(c).

answered Dec 16, 2018 at 23:57

José García

1

Comments

Unihedron · Accepted Answer · 2014-11-12 18:32:30Z

-4

if C object having null value then following statement used to compare null value:

if (c.toString() == null) {

    System.out.println("hello execute statement");

}

edited Nov 12, 2014 at 18:32

Unihedron

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answered Nov 12, 2014 at 18:16

shaik

1

1 Comment

user1071777 Over a year ago

Nope. c itself is null, so you'd get a NullPointerException.

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