Javaサンプル(絵ボタンクリックと文字列表示)

//Sample11.java
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingConstants;
public class Sample11 {
  private static final String bt01_filename = "twinstar.gif";
  private static final String bt02_filename = "pink.gif";
  private static final String bt03_filename = "white.gif";
  private static final String b0_title = "twin";
  private static final String b1_title = "pink";
  private static final String b2_title = "white";
  private static final String window_title = "絵ボタンクリックと文字列表示";
  private static final int position_X = 50;
  private static final int position_Y = 50;
  private static final int window_width = 300;
  private static final int window_height = 250;
  JLabel lbl = new JLabel("", SwingConstants.CENTER);
  // 主処理
  public static void main(final String args[]) {
    final Sample11 sample = new Sample11();
  }
  // コンストラクタ
  public Sample11() {
    // フレームを作成
    final JFrame f = new JFrame(Sample11.window_title);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    // ボタンを追加
    final JButton bt01 = new JButton(new ImageIcon(Sample11.bt01_filename));
    bt01.setActionCommand(Sample11.b0_title);
    final JButton bt02 = new JButton(new ImageIcon(Sample11.bt02_filename));
    bt02.setActionCommand(Sample11.b1_title);
    final JButton bt03 = new JButton(new ImageIcon(Sample11.bt03_filename));
    bt03.setActionCommand(Sample11.b2_title);
    // ボタンにアクションリスナを登録
    bt01.addActionListener(new PushButtonActionListener());
    bt02.addActionListener(new PushButtonActionListener());
    bt03.addActionListener(new PushButtonActionListener());
    // ボタンとラベルをレイアウト
    final JPanel p = new JPanel();
    p.add(bt01);
    p.add(bt02);
    p.add(bt03);
    f.getContentPane().add(p, BorderLayout.NORTH);
    f.getContentPane().add(this.lbl, BorderLayout.CENTER);
    // フレームを表示
    f.setBounds(Sample11.position_X, Sample11.position_Y,
        Sample11.window_width, Sample11.window_height);
    f.setVisible(true);
  }
  // ボタンクリック時のアクションリスナ
  private class PushButtonActionListener implements ActionListener {
    private static final String s1 = "星がふたつです。";
    private static final String s2 = "だんだら模様のぎざぎざ四角。";
    private static final String s3 = "白くって小さな丸がみっつ。";
    public void actionPerformed(final ActionEvent ae) {
      if (ae.getActionCommand().equals(Sample11.b0_title)) {
        Sample11.this.lbl.setText(PushButtonActionListener.s1);
      } else if (ae.getActionCommand().equals(Sample11.b1_title)) {
        Sample11.this.lbl.setText(PushButtonActionListener.s2);
      } else if (ae.getActionCommand().equals(Sample11.b2_title)) {
        Sample11.this.lbl.setText(PushButtonActionListener.s3);
      }
    }
  }
}