Null Pointer Exception at JLabel Array

Question

I want to create JLabel with icon in for loop.

Here is my code;

 final JLabel[] box = new JLabel[27]; 
 for(int i = 0; i < 25; i++){
     int j = 1;
     String r = "case" + j + ".png";
     box[i] = new JLabel(new ImageIcon(getClass().getResource(r)));
     j++;
 }

names of icons are like case1.png, case2.png;....

But there is a null point exception.

Exception in thread "main" java.lang.NullPointerException at 
java.awt.Container.addImpl(Unknown Source) at java.awt.Container.add(Unknown Source)
at Game.<init>(Game.java:185) at Game.main(Game.java:243) here are the exceptions

Is it just because I did not create names of icons truely? Thanks in advance.

for a quick reply check if your box is initialised. you should post your complete error log here for us to track the null pointer. — madteapot
– madteapot, Commented Apr 5, 2014 at 11:44
final JLabel[] box= new JLabel[27]; I initialised it like that is there any problem? — user3075117
– user3075117, Commented Apr 5, 2014 at 11:47
Exception in thread "main" java.lang.NullPointerException at java.awt.Container.addImpl(Unknown Source) at java.awt.Container.add(Unknown Source) at Game.<init>(Game.java:185) at Game.main(Game.java:243) here are the exceptions — user3075117
– user3075117, Commented Apr 5, 2014 at 11:49
This probably has nothing to do with your problem, but do note that j is always equal to 1, so all icons will be initialized from "case1.png". — Rudi Angela
– Rudi Angela, Commented Apr 5, 2014 at 12:04

nubteens · Accepted Answer · 2014-04-05 12:10:28Z

2

You are declaring ALL your JLabel's name as case1.png since at the start of your for loop, you are assigning int j = 1;

Your code should look like this:

 final JLabel[] box = new JLabel[27]; 
 int j = 1; //should be outside the for loop
 for(int i = 0; i < 25; i++) {
     String r = "case" + j + ".png";
     box[i] = new JLabel(new ImageIcon(getClass().getResource(r)));
     j++;
 }

answered Apr 5, 2014 at 12:10

nubteens

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1 Comment

user3075117 Over a year ago

thanx :) it work but I found the problem. in for loop instead of i<25 i should do i<26 :DDDDD

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