Making Your Own Exception Classes

• The fun does not stop there.  You can make your own Exception classes and throw them.
• Let's make an Exception called ListNotLongEnoughException.  We'll throw this from our example instead of the general Exception we have been throwing.
• We'll extend Exception, so we'll be given the methods that Exception already has.  This includes message() and printStackTrace().
• We can add our own methods, like setNumberOfElements() and getNumberOfElements().  We can use these methods when we instantiate and catch this exception.
• With Forte', choose New-Classes-Exception.
• The source code for this is:


/*
 * ListNotLongEnough.java
 *
 * Created on April 1, 2002, 9:15 PM
 */

/**
 *
 * @author  jonesbr@email.uc.edu
 */
public class ListNotLongEnoughException extends java.lang.Exception {

    // Number of items in the list.
    int numberOfItems;
 
    /**
     * Creates a new instance of <code>ListNotLongEnough</code> without detail message.
     */
    public ListNotLongEnoughException() {
    }
 

    /**
     * Constructs an instance of <code>ListNotLongEnough</code> with the specified detail message.
     * @param msg the detail message.
     */
    public ListNotLongEnoughException(String msg) {
        super(msg);
    }
 
    /**
     * setNumberOfItems
     * Sets the number of items in the list.
     *
     * @param numberOfItems the number of items in the list.
     *
     */
 
    public void setNumberOfItems(int numberOfItems) {
        this.numberOfItems = numberOfItems;
    }
 
    /**
     * getNumberOfItems
     * Gets the number of items in the list.
     *
     * @return the number of items.
     */
 
    public int getNumberOfItems() {
        return numberOfItems;
    }
 
}
 
 

• We'll use this in just a few moments.

Created by:  Brandan Jones December 17, 2001