You can override the paintComponent
method in JXTable. The following example creates a JTable with a line thickness of 3 pixels after the 2nd row:
JXTable table = new JXTable() {
protected void paintComponent(Graphics g) {
super.paintComponent(g);
// Actual line thickness is: thickness * 2 + 1
// Increase this as you wish.
int thickness = 1;
// Number of rows ABOVE the thick line
int rowsAbove = 2;
g.setColor(getGridColor());
int y = getRowHeight() * rowsAbove - 1;
g.fillRect(0, y - thickness, getWidth(), thickness * 2 + 1);
};
};