Javaサンプル(ボタンクリックとテキストフィールド表示)

//Sample23
import java.applet.Applet;
import java.awt.Button;
import java.awt.Graphics;
import java.awt.Label;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Sample23 extends Applet implements ActionListener {
  private static final String window_title = "ボタンクリックとテキストフィールド表示";
  private static final int window_width = 420;
  private static final int window_height = 200;
  private static final String b01_title = "A to B";
  private static final String b02_title = "B to A";
  private static final String data1 = "ああああ";
  private static final String data2 = "いいいいいいいいいい";
  private static final int tf01_size = 60;
  private static final int tf02_size = 20;
  private static final long serialVersionUID = 1L;
  Button b01;
  Button b02;
  TextField tf01 = new TextField("", Sample23.tf01_size);
  TextField tf02 = new TextField("", Sample23.tf02_size);
  int flg_button = -1;
  // 初期処理
  @Override
  public void init() {
    this.setSize(Sample23.window_width, Sample23.window_height);
    this.add(new Label(Sample23.window_title));
    this.b01 = new Button(Sample23.b01_title);
    this.b02 = new Button(Sample23.b02_title);
    this.add(this.b01);
    this.add(this.b02);
    this.add(this.tf01);
    this.add(this.tf02);
    this.b01.addActionListener(this);
    this.b02.addActionListener(this);
  }
  // 描画
  @Override
  public void paint(final Graphics g) {
    if (this.flg_button == -1) {
      this.tf01.setText("");
      this.tf02.setText("");
    }
    if (this.flg_button == 0) {
      this.tf01.setText(Sample23.data1);
      this.tf02.setText(Sample23.data2);
    }
    if (this.flg_button == 1) {
      this.tf01.setText(Sample23.data2);
      this.tf02.setText(Sample23.data1);
    }
  }
  // イベント
  public void actionPerformed(final ActionEvent ae) {
    if (ae.getSource() == this.b01) {
      this.flg_button = 0;
      this.repaint();
    }
    if (ae.getSource() == this.b02) {
      this.flg_button = 1;
      this.repaint();
    }
  }
}