Null Pointer Exception in If condition

Question

     Product p = dao.checkProduct(pnumber);
     ExpensiveProduct ep = dao.checkexpensiveProduct(pnumber);
     if ((p.getNumber() == null)&&(ep.getNumber()==null) ){ // java.lang.NullPointerException 
     //do something

     }else{
    //do something

      }

Why this statement giving java.lang.NullPointerException Do I have any other way to check this?

Make sure p and ep are non-null before calling getNumber() on them. — FThompson
– FThompson, Commented Oct 21, 2012 at 17:03

Tomasz Nurkiewicz · Accepted Answer · 2012-10-21 17:04:18Z

3

The only non-trivial possibility where this code can throw NPE is pnumber being Integer where checkProduct() or checkexpensiveProduct() expects int (or similar).

Other trivial reasons are dao or p being null (easy to check).

answered Oct 21, 2012 at 17:04

Tomasz Nurkiewicz

342k72 gold badges713 silver badges680 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Amal Prasad Over a year ago

i need to check that nulls and get true on that statement can i && those 2?

duffymo · Accepted Answer · 2012-10-21 17:04:33Z

2

Try it like this:

if ((p != null) && (p.getNumber() == null) && (ep != null) && (ep.getNumber()==null) ){

answered Oct 21, 2012 at 17:04

duffymo

310k46 gold badges376 silver badges571 bronze badges

2 Comments

Amal Prasad Over a year ago

this always false i need to do else part also any idea to do that?

duffymo Over a year ago

If it's always false, I think you have your answer. Fix p and ep.

Pops · Accepted Answer · 2012-10-21 17:46:54Z

1

NullPointerExceptions (NPEs) occur when you call a method or access a property of a null object.

To check for nulls, you could print the values of your variables before you try to use them, or step through your program with a debugger and check what the variables' values are when you reach the line where the exception happens.

EDIT:
Regarding your comment

i need to check p.getNumber() and ep.getNumber() both returning null and get ture on that statement

your existing code

if ((p.getNumber() == null)&&(ep.getNumber()==null) )

is already doing that. Since you're getting an NPE on that line, p itself is null, or ep is null, or both. You should examine your checkProduct() and checkexpensiveProduct() methods, where p and ep are set, to see if they're working correctly.

edited Oct 21, 2012 at 17:46

answered Oct 21, 2012 at 17:04

Pops

31k37 gold badges139 silver badges153 bronze badges

4 Comments

Amal Prasad Over a year ago

i need to check that nulls and get true on that statement can i && those 2?

Pops Over a year ago

I don't understand your comment. Can you rephrase?

Amal Prasad Over a year ago

i need to check p.getNumber() and ep.getNumber() both returning null and get ture on that statement

Pops Over a year ago

I edited. In your program, does it ever make sense for p or ep to be null? Or would they only ever be null if something went wrong?

Hardik Mishra · Accepted Answer · 2012-10-22 07:47:04Z

1

check your p variable and ep variable .One of them is null.check why

 dao.checkProduct(pnumber)

or

dao.checkexpensiveProduct(pnumber); is returning null

edited Oct 22, 2012 at 7:47

Hardik Mishra

14.9k9 gold badges63 silver badges98 bronze badges

answered Oct 21, 2012 at 17:06

saum22

88212 silver badges28 bronze badges

Comments

Renato Lochetti · Accepted Answer · 2012-10-21 17:04:53Z

0

What line is giving the NullPointerException? Be sure that p or ep are not null.

answered Oct 21, 2012 at 17:04

Renato Lochetti

4,5863 gold badges34 silver badges50 bronze badges

4 Comments

Amal Prasad Over a year ago

i need to check those are returning null and get ture and do else part.

Renato Lochetti Over a year ago

If one of the objects is null, you can't use his methods like you did in your code. Check the methods dao.checkProduct() and dao.checkexpensiveProduct() to be sure that they will not return a null object. Instead, they can return a instatiated object without any attribute.

Amal Prasad Over a year ago

so you are saying if both return null its gonabe NullPointerException?

Renato Lochetti Over a year ago

If one method return null, the code will throw the NullPointerException because you are trying to acess a method within a null object. When you do p.getNumber(), if p is null, you'll get a NullPointerException. Same thing for the pe object.

Collectives™ on Stack Overflow

Null Pointer Exception in If condition

5 Answers 5

1 Comment

2 Comments

4 Comments

Comments

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

1 Comment

2 Comments

4 Comments

Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related