A Applet Class to Demonstrate a Sort Algorithm

package com.sun.example;
 
/* From http://java.sun.com/docs/books/tutorial/index.html */
 
/*
 * @(#)SortItem.java  1.17f 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 java.awt.Color;
import java.awt.Graphics;
 
/**
 * 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 1.17f, 10 Apr 1995
 */
public class SortItem extends java.applet.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[size().height / 2];
	double f = size().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();
	}
	try {
	    Thread.sleep(20);
	} catch (InterruptedException e) {
	}
    }
 
    /**
     * Initialize the applet.
     */
    public void init() {
	String at = getParameter("alg");
	if (at == null) {
	    at = "BubbleSort";
	}
 
	algName = at + "Algorithm";
	scramble();
 
	setBackground(Color.white);
 
	resize(100, 100);
    }
 
    /**
     * Paint the array of numbers as a list of horizontal lines of varying lenghts.
     */
    public void paint(Graphics g) {
	int[] a = arr;
	int y = size().height - 1;
 
	// Erase old lines
	g.setColor(Color.lightGray);
	for (int i = a.length; --i >= 0; y -= 2) {
	    g.drawLine(arr[i], y, size().width, y);
	}
 
	// Draw new lines
	g.setColor(Color.black);
	y = size().height - 1;
	for (int i = a.length; --i >= 0; y -= 2) {
	    g.drawLine(0, y, arr[i], y);
	}
 
	if (h1 >= 0) {
	    g.setColor(Color.red);
	    y = h1 * 2 + 1;
	    g.drawLine(0, y, size().width, y);
	}
	if (h2 >= 0) {
	    g.setColor(Color.blue);
	    y = h2 * 2 + 1;
	    g.drawLine(0, y, size().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) Class.forName(algName).newInstance();
		algorithm.setParent(this);
	    }
	    algorithm.init();
	    algorithm.sort(arr);
	} catch (Exception e) {
	}
    }
 
    /**
     * Stop the applet. Kill any sorting algorithm that is still sorting.
     */
    public synchronized void stop() {
	if (kicker != null) {
	    try {
		kicker.stop();
	    } catch (IllegalThreadStateException e) {
		// ignore this exception
	    }
	    kicker = null;
	}
	if (algorithm != null) {
	    try {
		algorithm.stop();
	    } catch (IllegalThreadStateException 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 boolean mouseUp(java.awt.Event evt, int x, int y) {
	startSort();
	return true;
    }
}
 
/*
 * @(#)BidirectionalBubbleSortAlgorithm.java 1.6f 95/01/31 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.
 */
 
/**
 * A bi-directional bubble sort demonstration algorithm SortAlgorithm.java, Thu Oct 27 10:32:35 1994
 * 
 * @author James Gosling
 * @version 1.6f, 31 Jan 1995
 */
 
class BidirectionalBubbleSortAlgorithm extends SortAlgorithm {
    void sort(int[] a) throws Exception {
	int j;
	int limit = a.length;
	int st = -1;
	while (st < limit) {
	    boolean flipped = false;
	    st++;
	    limit--;
	    for (j = st; j < limit; j++) {
		if (stopRequested) {
		    return;
		}
		if (a[j] > a[j + 1]) {
		    int T = a[j];
		    a[j] = a[j + 1];
		    a[j + 1] = T;
		    flipped = true;
		    pause(st, limit);
		}
	    }
	    if (!flipped) {
		return;
	    }
	    for (j = limit; --j >= st;) {
		if (stopRequested) {
		    return;
		}
		if (a[j] > a[j + 1]) {
		    int T = a[j];
		    a[j] = a[j + 1];
		    a[j + 1] = T;
		    flipped = true;
		    pause(st, limit);
		}
	    }
	    if (!flipped) {
		return;
	    }
	}
	pause(st, limit);
    }
}
 
/*
 * @(#)SortAlgorithm.java 1.6f 95/01/31 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.
 */
 
/**
 * A generic sort demonstration algorithm SortAlgorithm.java, Thu Oct 27 10:32:35 1994
 * 
 * @author James Gosling
 * @version 1.6f, 31 Jan 1995
 */
 
class SortAlgorithm {
    /**
     * The sort item.
     */
    private SortItem parent;
 
    /**
     * When true stop sorting.
     */
    protected boolean stopRequested = false;
 
    /**
     * Set the parent.
     */
    public void setParent(SortItem p) {
	parent = p;
    }
 
    /**
     * Pause for a while.
     */
    protected void pause() throws Exception {
	if (stopRequested) {
	    throw new Exception("Sort Algorithm");
	}
	parent.pause(parent.h1, parent.h2);
    }
 
    /**
     * Pause for a while and mark item 1.
     */
    protected void pause(int H1) throws Exception {
	if (stopRequested) {
	    throw new Exception("Sort Algorithm");
	}
	parent.pause(H1, parent.h2);
    }
 
    /**
     * Pause for a while and mark item 1 & 2.
     */
    protected void pause(int H1, int H2) throws Exception {
	if (stopRequested) {
	    throw new Exception("Sort Algorithm");
	}
	parent.pause(H1, H2);
    }
 
    /**
     * Stop sorting.
     */
    public void stop() {
	stopRequested = true;
    }
 
    /**
     * Initialize
     */
    public void init() {
	stopRequested = false;
    }
 
    /**
     * This method will be called to sort an array of integers.
     */
    void sort(int[] a) throws Exception {
    }
}
 
/*
 * @(#)QSortAlgorithm.java 1.6f 95/01/31 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.
 */
 
/**
 * A quick sort demonstration algorithm SortAlgorithm.java, Thu Oct 27 10:32:35 1994
 * 
 * @author James Gosling
 * @version 1.6f, 31 Jan 1995
 */
class QSortAlgorithm extends SortAlgorithm {
    void sort(int[] a, int lo0, int hi0) throws Exception {
	int lo = lo0;
	int hi = hi0;
	pause(lo, hi);
	if (lo >= hi) {
	    return;
	}
	int mid = a[(lo + hi) / 2];
	while (lo < hi) {
	    while (lo < hi && a[lo] < mid) {
		lo++;
	    }
	    while (lo < hi && a[hi] > mid) {
		hi--;
	    }
	    if (lo < hi) {
		int T = a[lo];
		a[lo] = a[hi];
		a[hi] = T;
		lo++;
		hi--;
		pause();
	    }
	}
	if (hi < lo) {
	    int T = hi;
	    hi = lo;
	    lo = T;
	}
	sort(a, lo0, lo);
	sort(a, lo == lo0 ? lo + 1 : lo, hi0);
    }
 
    void sort(int[] a) throws Exception {
	sort(a, 0, a.length - 1);
    }
}
 
/*
 * @(#)BubbleSortAlgorithm.java 1.6f 95/01/31 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.
 */
 
/**
 * A bubble sort demonstration algorithm SortAlgorithm.java, Thu Oct 27 10:32:35 1994
 * 
 * @author James Gosling
 * @version 1.6f, 31 Jan 1995
 */
class BubbleSortAlgorithm extends SortAlgorithm {
    void sort(int[] a) throws Exception {
	for (int i = a.length; --i >= 0;)
	    for (int j = 0; j < i; j++) {
		if (stopRequested) {
		    return;
		}
		if (a[j] > a[j + 1]) {
		    int T = a[j];
		    a[j] = a[j + 1];
		    a[j + 1] = T;
		}
		pause(i, j);
	    }
 
    }
}