How do we show the gridline in GridLayout?

Question

How do we show the gridline in GridLayout? in Java?

JPanel panel = new JPanel(new GridLayout(10,10));
panel.setBorder(BorderFactory.createEmptyBorder(2,2,2,2));

for (int i =0; i<(10*10); i++){
   panel.add(new JLabel("Label"));
}

Answer 1

I would try to do it by adding borders to the components as they are added. The simple way to do it is just using BorderFactory.createLineBorder(), like this:

JPanel panel = new JPanel(new GridLayout(10,10));
panel.setBorder(BorderFactory.createEmptyBorder(2,2,2,2));

for (int i =0; i<(10*10); i++){
    final JLabel label = new JLabel("Label");
    label.setBorder(BorderFactory.createLineBorder(Color.BLACK));
    panel.add(label);
}

However, that will give you thicker borders between the cells than at the edges of the panel, because the outer edges will only have a one-pixel thick border and the inside edges will have two one-pixel thick borders together. To work around that, you can use BorderFactory.createMatteBorder() to only draw one-pixel-wide borders everywhere:

final int borderWidth = 1;
final int rows = 10;
final int cols = 10;
JPanel panel = new JPanel(new GridLayout(rows, cols));
panel.setBorder(BorderFactory.createEmptyBorder(2,2,2,2));

for (int row = 0; row < rows; row++) {
    for (int col = 0; col < cols; col++) {
        final JLabel label = new JLabel("Label");
        if (row == 0) {
            if (col == 0) {
                // Top left corner, draw all sides
                label.setBorder(BorderFactory.createLineBorder(Color.BLACK));
            }
            else {
                // Top edge, draw all sides except left edge
                label.setBorder(BorderFactory.createMatteBorder(borderWidth, 
                                                                0, 
                                                                borderWidth, 
                                                                borderWidth, 
                                                                Color.BLACK));
            }
        }
        else {
            if (col == 0) {
                // Left-hand edge, draw all sides except top
                label.setBorder(BorderFactory.createMatteBorder(0, 
                                                                borderWidth, 
                                                                borderWidth, 
                                                                borderWidth, 
                                                                Color.BLACK));
            }
            else {
                // Neither top edge nor left edge, skip both top and left lines
                label.setBorder(BorderFactory.createMatteBorder(0, 
                                                                0, 
                                                                borderWidth, 
                                                                borderWidth, 
                                                                Color.BLACK));
            }
        }
        panel.add(label);
    }
}

This should give you borders of width borderWidth everywhere, both between cells and along the outside edges.

Answer 2

There is an easier work around to the thick borders problem mentioned by Joe Carnahan: GridLayout(10,10, -1, -1) sets the vertical gaps and the horizontal gaps between components to -1. So the full code is:

JPanel panel = new JPanel(new GridLayout(10,10, -1, -1));
panel.setBorder(BorderFactory.createEmptyBorder(2,2,2,2));

for (int i =0; i<(10*10); i++){
    final JLabel label = new JLabel("Label");
    label.setBorder(BorderFactory.createLineBorder(Color.BLACK));
    panel.add(label);
}