Javaサンプル(ひよこがいっぱい)

//Sample18
import java.awt.GridLayout;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingConstants;
public class Sample18 {
  private static final String window_title = "ひよこがいっぱい（クリックしてください）";
  private static final int window_width = 640;
  private static final int window_height = 400;
  private static final int image_kind_cnt = 7;
  JLabel[] lbl = new JLabel[32];
  int cnt = 0;
  // 主処理
  public static void main(final String ar[]) {
    final Sample18 sample = new Sample18();
  }
  // コンストラクタ
  public Sample18() {
    // フレームを作成
    final JFrame f = new JFrame(Sample18.window_title);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    final JPanel p = new JPanel();
    p.setLayout(null);
    // ひよこラベルを32個作る
    for (int i = 0; i < this.lbl.length; i++) {
      final String imgname = "cut"
          + (int) (Math.random() * Sample18.image_kind_cnt) + ".gif";
      final Icon img = new ImageIcon(imgname);
      this.lbl[i] = new JLabel("", img, SwingConstants.LEFT);
      p.add(this.lbl[i]);
    }
    // マウスリスナを追加
    p.addMouseListener(new myMouseListener());
    // フレームに追加
    f.getContentPane().add(p);
    // フレームを表示
    f.setSize(Sample18.window_width, Sample18.window_height);
    f.getContentPane().setLayout(new GridLayout(1, 1));
    f.setVisible(true);
  }
  // マウスイベントを受け取るリスナ
  class myMouseListener extends MouseAdapter {
    private static final int lbl_width = 72;
    private static final int lbl_height = 88;
    @Override
    public void mouseClicked(final MouseEvent me) {
      Sample18.this.cnt = Sample18.this.cnt + 1;
      if (Sample18.this.cnt == Sample18.this.lbl.length) {
        Sample18.this.cnt = 0;
      }
      final int x = me.getX();
      final int y = me.getY();
      Sample18.this.lbl[Sample18.this.cnt].setBounds(x
          - myMouseListener.lbl_width / 2, y
          - myMouseListener.lbl_height / 2,
          myMouseListener.lbl_width, myMouseListener.lbl_height);
    }
  }
}