Java - NullPointerException in Array

Question

I have encountered the following problem: I have a java class with a private member like so:

private Arcs[] arcs;

This is not initialised i

Answer 1

Are you actually ever storing an Arcs object in arcs[i]? If not, all elements of arcs[] will be initialized to null. (Hence the NPE)

Do something like this:

while(condition){
    // ...
    arcs[i] = new Arcs();
    arcs[i].add(blah); 
    // ...
}

Reference:

• Java Tutorial: Arrays