GridLayoutPane.java

import javax.swing.*;
import java.awt.*;

public class GridLayoutPane {
 public static void main(String[] args) {
 JFrame frame = new JFrame("GridLayoutPane");
 JPanel panel = new JPanel();
 panel.setLayout(new GridLayout(0,3,10,10));
 panel.setPreferredSize(new Dimension(450,150));
 frame.getContentPane().add(panel);

 //add button to desontrate the layout
 for (int i = 1; i<= 12; i++)
 panel.add(new JButton("Button #"+i));

 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 frame.pack();
 frame.setVisible(true);
 }
}