addingmachine.java

Java程序设计技巧与开发实例附书源代码。

import java.applet.*;
import java.awt.*;
import java.awt.event.*;

public class AddingMachine
    extends Applet
    implements ActionListener {
  private Button addButton = new Button("Add");
  private Button subButton = new Button("Subtract");
  private Button resetButton = new Button("Reset");
  private TextField input = new TextField(10);
  private TextField output = new TextField(10);
  private double total = 0;

  public void init() {
    setLayout(new FlowLayout());
    add(addButton);
    add(subButton);
    add(input);
    add(resetButton);
    add(output);
    addButton.addActionListener(this);
    subButton.addActionListener(this);
    resetButton.addActionListener(this);
    handleReset();
    input.addKeyListener(new AddingMachineKeyHandler(this));
  }

  public void handleAdd() {
    total += Double.valueOf(input.getText().trim()).doubleValue();
    output.setText(String.valueOf(total));
  }

  private void handleSubtract() {
    total -= Double.valueOf(input.getText().trim()).doubleValue();
    output.setText(String.valueOf(total));
  }

  private void handleReset() {
    total = 0.0;
    input.setText("0.0");
    output.setText("0.0");
  }

  public void actionPerformed(ActionEvent e) {
    if (e.getSource() == addButton) {
      handleAdd();
    }
    else if (e.getSource() == subButton) {
      handleSubtract();
    }
    else if (e.getSource() == resetButton) {
      handleReset();
    }
  }
}