/* Copyright 2003 by Lawrence Kesteloot */package com.teamten.a;/** * Keeps a fixed-length queue of characters.  There are only three * operations on the queue: set the whole thing; append a character * (dropping the first); and retreive the whole thing.  This is useful * as a moving window on a text stream. */class CharQueue{    private int length;    private char[] queue;    private int count;    /**     * Create the queue with a fixed length.  The queue will be     * filled with the value 0, so don't use the toString()     * method until the queue has been filled with either     * set() or put().     */    public CharQueue(int length)    {        this.length = length;        queue = new char[length];        count = 0;    }    /**     * Sets the contents of the queue.  The length of the string     * must be the same as the length passed to the constructor.     */    public void set(String s)    {        if (s.length() != length)        {            System.out.println("Lengths don't match");            return;        }        queue = s.toCharArray();        count = length;    }    /**     * Appends the character to the queue.  If the resulting queue     * would be longer than the length set in the constructor, then     * the first character is dropped.     */    public void put(char c)    {        if (count == length)        {            System.arraycopy(queue, 1, queue, 0, length - 1);            count--;        }        queue[count++] = c;    }    /**     * Returns the contents of the queue as a string.  This does     * not take into account the number of characters that have     * been put into the queue.  The returned string's length     * is always the length passed to the constructor.     */    public String toString()    {        return new String(queue);    }}