Chip: Internet/Chip Internet.iso/wwwutil/hotjava.ins/hotjava.exe/hotjava/demo/classes/SortItem.java

Text File | 1995-05-19 | 5KB | 236 lines

/*
 * @(#)SortItem.java    1.17 95/04/10 James Gosling
 *
 * Copyright (c) 1994 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this software
 * and its documentation for NON-COMMERCIAL purposes and without
 * fee is hereby granted provided that this copyright notice
 * appears in all copies. Please refer to the file "copyright.html"
 * for further important copyright and licensing information.
 *
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
 * THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
 * TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR
 * ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
 * DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
 */

import awt.*;
import browser.NameServer;
import java.io.InputStream;
import java.util.Hashtable;
import net.www.html.*;
import browser.Applet;

/**
 * A simple applet class to demonstrate a sort algorithm.
 * You can specify a sorting algorithm using the "alg"
 * attribyte. When you click on the applet, a thread is
 * forked which animates the sorting algorithm.
 *
 * @author James Gosling
 * @version     1.17, 10 Apr 1995
 */
public
class SortItem extends Applet implements Runnable {
    /**
     * The thread that is sorting (or null).
     */
    private Thread kicker;

    /**
     * The array that is being sorted.
     */
    int arr[];

    /**
     * The high water mark.
     */
    int h1 = -1;

    /**
     * The low water mark.
     */
    int h2 = -1;

    /**
     * The name of the algorithm.
     */
    String algName;

    /**
     * The sorting algorithm (or null).
     */
    SortAlgorithm algorithm;

    /**
     * Fill the array with random numbers from 0..n-1.
     */
    void scramble() {
    int a[] = new int[height / 2];
    double f = width / (double) a.length;
    for (int i = a.length; --i >= 0;) {
        a[i] = (int)(i * f);
    }
    for (int i = a.length; --i >= 0;) {
        int j = (int)(i * Math.random());
        int t = a[i];
        a[i] = a[j];
        a[j] = t;
    }
    arr = a;
    }

    /**
     * Pause a while.
     * @see SortAlgorithm
     */
    void pause() {
    pause(-1, -1);
    }

    /**
     * Pause a while, and draw the high water mark.
     * @see SortAlgorithm
     */
    void pause(int H1) {
    pause(H1, -1);
    }

    /**
     * Pause a while, and draw the low&high water marks.
     * @see SortAlgorithm
     */
    void pause(int H1, int H2) {
    h1 = H1;
    h2 = H2;
    if (kicker != null) {
        repaint();
    }
    Thread.sleep(20);
    }

    /**
     * Initialize the applet.
     */
    public void init() {
    resize(100, 100);

    String at = getAttribute("alg");
    if (at == null) {
        at = "BubbleSort";
    }

    algName = at + "Algorithm";
    scramble();
    }

    /**
     * Paint the array of numbers as a list
     * of horizontal lines of varying lenghts.
     */
    public void paint(Graphics g) {
    int a[] = arr;
    int y = height - 1;

    // Erase old lines
    g.setForeground(Color.lightGray);
    for (int i = a.length; --i >= 0; y -= 2) {
        g.drawLine(arr[i], y, width, y);
    }

    // Draw new lines
    g.setForeground(Color.black);
    y = height - 1;
    for (int i = a.length; --i >= 0; y -= 2) {
        g.drawLine(0, y, arr[i], y);
    }

    if (h1 >= 0) {
        g.setForeground(Color.red);
        y = h1 * 2 + 1;
        g.drawLine(0, y, width, y);
    }
    if (h2 >= 0) {
        g.setForeground(Color.blue);
        y = h2 * 2 + 1;
        g.drawLine(0, y, width, y);
    }
    }

    /**
     * Update without erasing the background.
     */
    public void update(Graphics g) {
    paint(g);
    }

    /**
     * Run the sorting algorithm. This method is
     * called by class Thread once the sorting algorithm
     * is started.
     * @see java.lang.Thread#run
     * @see SortItem#mouseUp
     */
    public void run() {
    try {
        if (algorithm == null) {
        algorithm = (SortAlgorithm)new(algName);
        algorithm.setParent(this);
        }
        algorithm.init();
        algorithm.sort(arr);
    } catch(Object e) {
    }
    }

    /**
     * Stop the applet. Kill any sorting algorithm that
     * is still sorting.
     */
    public synchronized void stop() {
    if (kicker != null) {
            try {
        kicker.stop();
            } catch (IllegalStateException e) {
                // ignore this exception
            }
        kicker = null;
    }
    if (algorithm != null){
            try {
        algorithm.stop();
            } catch (IllegalStateException e) {
                // ignore this exception
            }
    }
    }


    /**
     * For a Thread to actually do the sorting. This routine makes
     * sure we do not simultaneously start several sorts if the user
     * repeatedly clicks on the sort item.  It needs to be
     * synchronoized with the stop() method because they both
     * manipulate the common kicker variable.
     */
    private synchronized void startSort() {
    if (kicker == null || !kicker.isAlive()) {
        scramble();
        repaint();
        kicker = new Thread(this);
        kicker.start();
    }
    }


    /**
     * The user clicked in the applet. Start the clock!
     */
    public void mouseUp(int x, int y) {
    startSort();
    }
}