Undefined behaviour of GridLayout

Question

I have created a GridLayout(3,2) in Java and inserted 6 JLabel components. They should be inserted in order of the code written, but they are arranged in descending order. Why?

import java.awt.GridLayout;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class Summary_Graph_JPanel1 extends JPanel {
    public Summary_Graph_JPanel1() {
        GridLayout g=new GridLayout(3,2);
        setLayout(g);
        add(new JLabel("1"),JLabel.CENTER);
        add(new JLabel("2"),JLabel.CENTER);
        add(new JLabel("3"),JLabel.CENTER);
        add(new JLabel("4"),JLabel.CENTER);
        add(new JLabel("5"),JLabel.CENTER);
        add(new JLabel("6"),JLabel.CENTER);
    }
}

This is how it looks:

Answer 1

The use of JLabel.CENTER is in the wrong place. It should be within the JLabel constructor rather than handed to the add(JLabel, constraint) method. It is not an appropriate constraint of the layout, but of the label.

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

public class Summary_Graph_JPanel1 extends JPanel {
    public Summary_Graph_JPanel1() {
        GridLayout g=new GridLayout(3,2);
        setLayout(g);
        add(new JLabel("1",JLabel.CENTER));
        add(new JLabel("2",JLabel.CENTER));
        add(new JLabel("3",JLabel.CENTER));
        add(new JLabel("4",JLabel.CENTER));
        add(new JLabel("5",JLabel.CENTER));
        add(new JLabel("6",JLabel.CENTER));
    }

    public static void main(String[] args) {
        JOptionPane.showMessageDialog(null, new Summary_Graph_JPanel1());
    }
}