Null point exception

Question

1.00/5 (1 vote)

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C#

try{
            AccountDAOImpl adi = new AccountDAOImpl();
            Account a = new Account();
            a = adi.getAccount(account, depositamt);
            a.setBalance(a.getBalance() + a.getDepositamt());
            adi.update(account);
            }catch(Exception ex){
                ex.printStackTrace();
            }
}

im getting a null point exception in above code 5th line.-> a.setBalance(a.getBalance() + a.getDepositamt());

Please tell me a solution for this

Updates by OP(3h later)
can I do this :

Java

if(a!=null){
            a.setBalance(a.getBalance() + a.getDepositamt());
            adi.update(account);
            }else {
                adi.update(account);
            }

Posted 13-Jun-13 18:24pm

mali_angel

Updated 13-Jun-13 23:05pm

TorstenH.

v2

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[no name] 3-Feb-14 2:11am

why we should handle the NullpointerException in if block only why not in trycatch block.give me the answer

3 solutions

Solution 2

can I do this :

C#

if(a!=null){
            a.setBalance(a.getBalance() + a.getDepositamt());
            adi.update(account);
            }else {
                adi.update(account);
            }

Posted 13-Jun-13 22:16pm

mali_angel

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_Amy · Accepted Answer · 2013-06-13T18:36:00

You should understand the basics first. Following are the possible causes when program throws NullPointerException[^].

When you call instance method on a null object. you won't get null pointer exception if you call static method or class method on null object because static method doesn't require an instance to call any method.
While accessing or changing any variable or field on null object.
Throwing null when an Exception is expected to throw.
When calling length of array when array is null.
Accessing or changing slots of null just like an array.
When you try to synchronize on null object or using null inside synchronized block in Java

Following are the checkpoints to resolve this issue:

Identify the line where it occurred.
Ask "what objects (or arrays) are being referenced on this line". One of them is null and it's usually obvious which.
Figure out why it's null.

You can also check:
How to : Avoid Null Pointer Exception in Java[^]
Why do I get a NullPointerException?[^]

--Amit

TorstenH. · Accepted Answer · 2013-06-13T23:03:00

Solution 3

What you can do is debugging:

Debugging with Eclipse[^]

Debugging with Netbeans[^]

Seams like one of the values is NULL:

- a (whatever "a" is... please use better names)
- return value of a.getBalance()
- return value of a.getDepositamt()

So you should check the values by debugging.

Posted 13-Jun-13 23:03pm