sortitem.java

java程序设计

/*
 * @(#)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.*;
import java.io.InputStream;
import java.util.Hashtable;
import java.net.*;

/**
 * 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[getSize().height / 2];
      double f = getSize().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 = getSize().height - 1;

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

      // Draw new lines
      g.setColor(Color.black);
      y = getSize().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, getSize().width, y);
      }
      if (h2 >= 0) {
          g.setColor(Color.blue);
          y = h2 * 2 + 1;
          g.drawLine(0, y, getSize().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() {
      Thread myThread = Thread.currentThread(); 
      while (kicker == myThread) { 
         try {
          if (algorithm == null) {
            algorithm = (SortAlgorithm)Class.forName(algName).newInstance();
            algorithm.setParent(this);
          }
          algorithm.init();
          algorithm.sort(arr);
          return;
         } catch(Exception e) {
         }
                  
      }
   }

    /**
     * Stop the applet. Kill any sorting algorithm that
     * is still sorting.
     */
    public synchronized void stop() {
      if (kicker != null) {
         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;
    }
}