gcs.java

利用BlueJ开发的一个类似小时候完的吃豆豆的小游戏

/*
 * cs101 Graphical Counting Semaphore utility
 * $Id: GCS.java,v 1.1.1.1 2002/06/05 21:56:32 root Exp $
 *
 * Developed for "Rethinking CS101", a project of Lynn Andrea Stein's AP Group.
 * For more information, see <a href="http://www.ai.mit.edu/projects/cs101/">the
 * CS101 homepage</a> or email <[e-mail]>.
 *
 * Copyright (C) 1996 Massachusetts Institute of Technology.
 * Please do not redistribute without obtaining permission.
 */

package cs101.util.semaphore;

import java.awt.*;
import cs101.awt.ColorField;

/**
 * cs101.util.GCS implements a counting semaphore of arbitrary size
 * in java. <br>
 * Interface is gcs.request(), gcs.release(). <br>
 * It also provides a graphical display of the semaphores status.
 * <p>
 * The general design of this utility was influenced by the 
 * design of the cs101.util.BS (wrote by Lynn Stein).
 * <br>
 * Copyright 1996 Massachusetts Institute of Technology
 *
 * @author  Todd C. Parnell, [e-mail]
 * @author  Joshua R. Brown, [e-mail] 
 * @version $Id: GCS.java,v 1.1.1.1 2002/06/05 21:56:32 root Exp $
 *
 */
public class GCS extends GraphicalSemaphore {
  /** the length of the semaphore */
  private int size;   
  /** how much of the semaphore is in use */
  private int busy;       // i <= busy are busy 
                          // ( ie if busy=size-1 then all busy )
  private ColorField[] fields;  
 
  //  GCS( int, int, String )
  /**
   * Constructs a counting semaphore with the size and initial value 
   * passed in.  
   * Uses the String past in to identfy the semaphore in the display.
   *
   * @param size     The length of the semaphore (Probably the length 
   *		     of the buffer that it is associated with).
   * @param busy     The number of intially busy blocks in the semaphore
   *                 (ie all busy = size, all free = 0).
   * @param label    An identfying string of text for the semaphore.
   */
  public GCS (int size, int busy, String label) {
    super(label);
    this.size = size;
    this.busy = busy-1;  // adjust for ease of use

    // make sure busy < size
    if (this.busy >= this.size) 
      this.busy = this.size-1;

    // make sure busy >= -1
    if (this.busy < -1)
      this.busy = -1;

    // now that everything is initialized setup the GUI
    this.setupGUI();

  }

  /**
   * Does all of the graphical setup on this level
   * then calls the superclasses method to finish the setup.
   *
   * This method is primarly responsible for setting up the 
   * display Panel.
   */
  protected void setupGUI() {

    // do setup on this level
    this.fields = new ColorField[this.size];
  
    display = new Panel();
    GridBagLayout layout = new GridBagLayout();
    display.setLayout(layout);
  
    GridBagConstraints con = new GridBagConstraints();
    con.gridwidth = 1; con.gridheight=1;
    con.fill = GridBagConstraints.VERTICAL;
    con.weightx = 0; con.weighty = 1/this.size;

    for (int i = 0; i < this.size; i++) {
      if (i <= this.busy)
	this.fields[i] = new ColorField(true, new Dimension(25,10),
				     Color.red, Color.green);
      else 
	this.fields[i] = new ColorField(false, new Dimension(25,10),
				     Color.red, Color.green);
      con.gridx = 0; con.gridy = i;
      layout.setConstraints(this.fields[i], con);
      display.add(this.fields[i]);

    }
    
    // now that GUI setup on this level is finished
    // call super-class method
    super.setupGUI();

  }

  /**
   * Requests the semaphore.  If all of the locks in the semaphore are
   * currently busy, causes the requesting process to wait() until
   * the semaphore is release()d.
   * Unlike java.lang.Object.wait(), the requesting process is not
   * suspended if the semaphore is currently free.
   *
   * @see #release
   * @see java.lang.Object#wait
   */
  synchronized public void request() {
    while (this.busy == this.size-1) {
      try {this.wait();} catch (InterruptedException e) {}
    }
    this.busy++;
    this.showStatus();
  }

  /**
   * Releases a lock of the semaphore (if any are currently busy).
   * Any objects currently wait()ing on the
   * semaphore are notify()d (and one of them will be granted the
   * semaphore).  Unlike java.lang.Object.notify(), the semaphore is
   * also freed so that if there are no wait()ing objects, the next
   * object to request() the semaphore will receive it.
   *
   * @see #request
   * @see java.lang.Object#notifyAll()
   */
  synchronized public void release () {
    if (this.busy >= 0) {
      this.busy--;
      this.notifyAll();
      this.showStatus();
    }
  }

  /**
   * Prints out the current state of the semaphore.
   * Changes the graphical display.
   */
  protected void showStatus() {      
    // tab over an approprate amount
    for (int i = 0; i<this.myNumber; i++) 
      System.out.print("               ");
    
    // now print the status 
    System.out.print(this.label.getText()+": ");
    System.out.println(this.busy+1);

    // update the status fields
    for (int i = 0; i < this.size; i++) {
      if (i <= this.busy)
	this.fields[i] .changeState(true);
      else 
	this.fields[i].changeState(false);
    }

  }

}

/* Comments:
 *
 * History:
 *     $Log: GCS.java,v $
 *     Revision 1.1.1.1  2002/06/05 21:56:32  root
 *     CS101 comes to Olin finally.
 *
 *     Revision 1.1  2000/04/24 22:17:22  nathanw
 *     Bulk reorganization
 *
 *     Revision 1.4  1998/07/24 17:19:27  tparnell
 *     Placate new javadoc behavior
 *
 *     Revision 1.3  1998/07/22 18:18:56  tparnell
 *     migration from cs101.util to cs101.*
 *
 *     Revision 1.2  1998/06/03 19:43:36  tparnell
 *     update from Java 1.0 to 1.1
 *
 *     Revision 1.1  1998/03/13 22:18:13  tparnell
 *     Import from server crash.  I think the src and class files match up.
 *
 *     Revision 1.4  1996/08/01 18:26:24  reuben
 *     More javadoc tweaking (hopefully the final pass)
 *
 *     Revision 1.3  1996/07/25 18:27:42  reuben
 *     Added all kinds of comments.
 *     Compiled and tested.
 *
 */