ArrayList error, Exception in thread & ldquo; hand & rdquo; java.lang.NullPointerException


I'm very new to Java, and I seem to be getting some bizarre errors. I've looked everywhere for a solution, and all the solutions I've come across are identical to what I already have.

I've written a class to add a destination to an ArrayList, yet it's not working.

I'm getting this error: "Exception in thread "main" java.lang.NullPointerException"

Here's my code:

public void addDestination(String destination) {

and the code for the data I'm trying to add to the ArrayList is this:

String temp = "test";
Agent smith = new Agent();

It quits the program in the method, and does not add the destination to the array list. Anyone got any ideas as to why? Thanks in advance.

I'd initialised it to null in my default constructor, d'oh. Thanks everyone :-)

A good practice in Java is to initialize your Collection to empty Collection instead of null in your default constructor.