java - ListSelectionListener null pointer error -

i'm trying specific color specific category display on south jpanel nullpointerexeception error. doing wrong?

//this arrays holding category names , colors. 

try checking if selected index in list greater -1.

//this arrays holding category names , colors. string[] cati = {"ingen", "matställen", "skolor", "kyrkor", "kollektiv trafik"}; color[] colors = {color.white, color.blue, color.green, color.yellow, color.pink};  // inner class in super class.  class kategorifärg implements listselectionlistener {            public void valuechanged(listselectionevent event) {          if (kategorlista.getselectedindex() > -1) {             system.out.println("does work?");             syd.setbackground(colors[kategorilista.getselectedindex()]);             //syd south jpanel         }     } } 

-1 means no item in list selected. if error occurs on if statement, kategorlista null , needs initialized. sample code, provided, looks initialized it. otherwise, syd null , needs initialized.

if of running. in code provided.

öst.add(kategorilista); 

is öst initialized? error you're getting should have been pointing @ line of code causing error.

edit

based on code you've added... make these 2 lines of codes class variables

string[] cati = { "ingen", "matställen", "skolor", "kyrkor",         "kollektiv trafik" }; color[] colors = { color.white, color.blue, color.green, color.yellow,         color.pink }; 

you have them coded in contructor , cannot seen anywhere else in class. if have them declared class variables, in constructor change code to:

cati = { "ingen", "matställen", "skolor", "kyrkor",         "kollektiv trafik" }; colors = { color.white, color.blue, color.green, color.yellow,         color.pink }; 

i believe name call shadowing... original code, shadowed class variables, , local variables initialized instead of class variables.