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 { // fields
    private Button addButton = new Button("Add");
    private Button subButton = new Button("Subtract");
    private Button resetButton = new Button("Reset");
    private DoubleField input = new DoubleField(10);
    private DoubleField output = new DoubleField(10);
    private int total = 0;
    // methods
    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);
    }

    public void start() {
        reset();
    }

    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == addButton) {
            total += input.getNumber();
        }
        else if (e.getSource() == subButton) {
            total -= input.getNumber();
        }
        else if (e.getSource() == resetButton) {
            reset();
        }
        output.setNumber(total);
    }

    private void reset() {
        total = 0;
        input.setNumber(0);
        output.setNumber(0);
    }
}