The setMargin() method works for the top, right, and bottom insets but for
some reason does not work for the left inset. As demo with the following
program the buttons/checkboxes always align to the left margin.

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

public class rButton extends JFrame {

    rButton() {
Container c = getContentPane();
c.setLayout(new FlowLayout());

JPanel p1 = new JPanel();
JPanel p2 = new JPanel();
p1.setLayout(new BoxLayout(p1, BoxLayout.X_AXIS));
p2.setLayout(new BoxLayout(p2, BoxLayout.Y_AXIS));
c.add(p1);
c.add(p2);

        ImageIcon icon = new ImageIcon("./red-ball.gif");

        JRadioButton []rb1 = {
new JRadioButton("Insets = 40", icon),
new JRadioButton("Insets = 30"),
new JRadioButton("Insets = 20"),
new JRadioButton("Insets = 10")
};

JCheckBox cb1 = new JCheckBox("Insets = 15", icon);
JCheckBox cb2 = new JCheckBox("Insets = 15", icon);
cb1.setMargin(new Insets(15, 15, 15, 15));
cb2.setMargin(new Insets(15, 15, 15, 15));

rb1[0].setMargin(new Insets(10, 10, 10, 10));
rb1[1].setMargin(new Insets(20, 20, 20, 20));
rb1[2].setMargin(new Insets(30, 30, 30, 30));
rb1[3].setMargin(new Insets(40, 40, 40, 40));

        JRadioButton []rb2 = {
new JRadioButton("Insets = 40", icon),
new JRadioButton("Insets = 30"),
new JRadioButton("Insets = 20"),
new JRadioButton("Insets = 10")
};

rb2[0].setMargin(new Insets(10, 10, 10, 10));
rb2[1].setMargin(new Insets(20, 20, 20, 20));
rb2[2].setMargin(new Insets(30, 30, 30, 30));
rb2[3].setMargin(new Insets(40, 40, 40, 40));

for (int i = 0; i < 4; i++) {
p1.add(rb1[i]);
p2.add(rb2[i]);
}

p1.add(cb1);
p2.add(cb2);

p1.validate();
p2.validate();

pack();
setSize(800, 400);
setVisible(true);
addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent we) {
                System.exit(0);
            }
        });
    }

   public static void main(String argv[]) {
new rButton();
    }
}