Android: Issue during Arraylist declaration

Question

If I declare Arraylist like this-

private ArrayList nodeList;

then, while adding array into it, getting NullPointerException

Answer 1

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.