You have tried to access an object that has had it's pointer declared, but hasn't yet been created.
public class TestException { static String bob; public static void main(String[] args) { bib(); if access was here, there would be a not initialised error } private static void bib() { if(bob.equals("pie")) bob doesn't have a String yet - gives null pointer exception System.out.println("Bob is pie!"); } }