如何制作JCheckBoxes的2D数组？

Question

I have to make a 2D array of JCheckBoxes in Java. I'm using the code below, but when I try to set selected true:

checks[0][1].setSelected(true);

it says that checks[0][1] is null .

JCheckBox[][] checks = new JCheckBox[14][14];

for (int i = 0; i < 14; i++) {
    for (int j = 0; j < 14; j++) 
        this.add(new JCheckBox(""));

Answer 1

You have to create each JCheckBox in the array and then add it. I'd also suggest using named constants instead of magic numbers, like so:

final int NUM_BOXES = 14; // named constant
JCheckBox[][] checks = new JCheckBox[NUM_BOXES][NUM_BOXES];

for (int i = 0; i < NUM_BOXES; i++) {
    for (int j = 0; j < NUM_BOXES; j++) 
        checks[i][j] = new JCheckBox("");
        this.add(checks[i][j]);
    }
}