I create JButton loop with Array, but it's doesn't work

Question

i want to create button by loop as

1 2 3
4 5 6
7 8 9

but button have array2D when i write code is

private JButton cells[][];

// Constructor
public SliderGameFrame() {
    JPanel panel = new JPanel();
    this.add(panel);
    for (int i = 1; i <= cells.length; i++) {
        for (int j = 1; j <= cells.length; j++) {
            cells[i][j] = new JButton(" " + i);
            panel.add(cells[i][j]);
        }
    }
}

it's doesn't work and error massage is java.lang.NullPointerException

You never iniztialize your Array. – Jens Sep 23 '16 at 08:06 — Jens, Sep 23 '16 at 08:06

score 1 · Answer 1 · answered Sep 23 '16 at 08:07

1

Change:

    for (int i = 1; i <= cells.length; i++) {
        for (int j = 1; j <= cells.length; j++) {

into:

for (int i = 0; i < cells.length; i++) {
    for (int j = 0; j < cells.length; j++) {

Two-dimensional array's indices start from 0 to dimension-1.

answered Sep 23 '16 at 08:07

AhmadWabbi

2,253
1
20
35

it's doesn't work same ): – mr.B Sep 23 '16 at 08:09
oh god, Im sorry to told that I forgot to iniztialize Array. – mr.B Sep 23 '16 at 08:11
Well, even tough you forgot to initialize the array, your loops should be as I showed in the answer. It won't work otherwise. – AhmadWabbi Sep 23 '16 at 08:13

I create JButton loop with Array, but it's doesn't work

1 Answers1