CODEWITHSUNDEEP
javaandroidarraylistdeclaration
Avisek Chakraborty
Avisek Chakraborty

Reputation: 8309

Android: Issue during Arraylist declaration

If I declare Arraylist like this-

private ArrayList<Integer[]> nodeList;

then, while adding array into it, getting NullPointerException

But, if I change it to-

private ArrayList<Integer[]> nodeList= new ArrayList<Integer[]>();

-it works fine.

Why the first one fails!

Upvotes: 0

Views: 425

Answers (1)

amit
amit

Reputation: 178491

The first only declares a variable, but does not create the actual object. only when you use new, you actually create the object.

In java unlike C++, declaring a variable does not allocate a local variable of it. To actually create the object, you need to explicitly create it [in your example: by using the new keyword].
(*)Note that this is only true to reference types objects, and java primitives are created with declaration.

Upvotes: 3

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