CODEWITHSUNDEEP
java
luke
luke

Reputation: 3599

Java null pointer exception after checking if null

Can anybody explain how is it possible that I am getting null pointer exception thrown from this line of code:

if (data != null && data.isActive()) {

Body of method isActive() is just:

public Boolean isActive() 
{
  return active;
}

Thanks in advance.

Upvotes: 2

Views: 2770

Answers (1)

user784540
user784540

Reputation:

In java, there's a thing called autoboxing, when primitive values are wrapped by object types and vice versa.

So, in your code there is a method:

public Boolean isActive() 
{
  return active;
}

note, that you are returning Boolean (object type), not boolean (primitive type).

and return value is going to be used in your if statement.

if (data != null && data.isActive()) {

when java meets data.isActive() in your if statement, it tries to convert Boolean value to primitive boolean value, to apply it for your logical operation.

But your active variable inside of your isActive() method is null, so java is unable to unbox this variable to boolean primitive value, and you get Null pointer exception.

Upvotes: 13

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