intentionalerrors.java

Java程序设计技巧与开发实例附书源代码。

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

public class IntentionalErrors
        extends Frame
        implements ActionListener
{
    public Button nullVariable = new Button("Null Variable");
    public Button arrayIndex = new Button("Array index invalid");
    public Button stringIndex = new Button("Negative string index");
    public Button quit = new Button("Quit");
    private double A[] = new double[10];
    private String string = "Bert";
    private String nada = null;
    public IntentionalErrors()
    {
        setLayout(new GridLayout(4, 1));
        add(nullVariable);
        nullVariable.addActionListener(this);
        add(arrayIndex);
        arrayIndex.addActionListener(this);
        add(stringIndex);
        stringIndex.addActionListener(this);
        add(quit);
        quit.addActionListener(this);
        validate();
        pack();
        setVisible(true);
    }

    public void actionPerformed(ActionEvent e)
    {
        try
        {
            if (e.getSource() == quit)
            {
                System.exit(0);
            }
            else if (e.getSource() == nullVariable)
            {
                System.out.println(nada.substring(0, 3));
            }
            else if (e.getSource() == arrayIndex)
            {
                A[10] = 10;
            }
            else if (e.getSource() == stringIndex)
            {
                System.out.println(string.charAt( -1));
            }
        }
        catch (StringIndexOutOfBoundsException se)
        {
            System.out.println("incorrect string index");
        }
        catch (NullPointerException ne)
        {
            System.out.println("oops, a null pointer");
        }
        catch (ArrayIndexOutOfBoundsException ae)
        {
            System.out.println("incorrect array index");
        }
    }

    public static void main(String args[])
    {
        IntentionalErrors ie = new IntentionalErrors();
    }
}