Java Swing How to - Draw dynamic icon for JButton

Question

We would like to know how to draw dynamic icon for JButton.
Answer

/*www  . j av  a2s . com*/
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Container;
import java.awt.Graphics;
import java.awt.Polygon;

import javax.swing.Icon;
import javax.swing.JButton;
import javax.swing.JFrame;

public class Main {

  public static void main(String args[]) {
    JFrame frame = new JFrame();
    Container contentPane = frame.getContentPane();
    Icon normalIcon = new TriangleIcon(Color.red, TriangleIcon.State.NORMAL);
    Icon pressedIcon = new TriangleIcon(Color.red, TriangleIcon.State.PRESSED);
    Icon rolloverIcon = new TriangleIcon(Color.red, TriangleIcon.State.ROLLOVER);
    JButton b = new JButton("Button", normalIcon);
    b.setPressedIcon(pressedIcon);
    b.setRolloverIcon(rolloverIcon);
    b.setRolloverEnabled(true);
    contentPane.add(b, BorderLayout.NORTH);
    frame.setSize(300, 100);
    frame.show();
  }
}

class TriangleIcon implements Icon {
  String name;

  static class State {
    public static final int NORMAL = 0;

    public static final int PRESSED = 1;

    public static final int ROLLOVER = 2;

    private State() {
    }
  }

  int state;

  Color color;

  public TriangleIcon(Color c, int state) {
    color = c;
    this.state = state;
  }

  public int getIconWidth() {
    return 20;
  }

  public int getIconHeight() {
    return 20;
  }

  public void paintIcon(Component c, Graphics g, int x, int y) {
    g.setColor(color);
    Polygon p = new Polygon();
    if (state == State.NORMAL) {
      p.addPoint(x + (getIconWidth() / 2), y);
      p.addPoint(x, y + getIconHeight() - 1);
      p.addPoint(x + getIconWidth() - 1, y + getIconHeight() - 1);
    } else if (state == State.PRESSED) {

      p.addPoint(x, y);
      p.addPoint(x + getIconWidth() - 1, y);
      p.addPoint(x + (getIconWidth() / 2), y + getIconHeight() - 1);
    } else {
      p.addPoint(x, y);
      p.addPoint(x, y + getIconHeight() - 1);
      p.addPoint(x + getIconWidth() - 1, y + (getIconHeight() / 2));
    }
    g.fillPolygon(p);
  }
}