/*
 * $Id: AnimateObject.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 <las@ai.mit.edu>.
 *
 * Copyright (C) 1999 Massachusetts Institute of Technology.
 * Please do not redistribute without obtaining permission.
 */
package cs101.util;

import cs101.lang.*;

/**
 * The generic self-animating (active) object.  Extend it, overriding
 * its act() method, to generate interesting behavior.
 *
 * Copyright 1999 Massachusetts Institute of Technology
 *
 * @see cs101.lang.AnimatorThread
 * @see cs101.lang.Animate
 *
 * @author Lynn Andrea Stein, las@ai.mit.edu
 * @version $Id: AnimateObject.java,v 1.1.1.1 2002/06/05 21:56:32 root Exp $
 *
 */

public abstract class AnimateObject extends Object implements Animate 
{
  /* CONSTANTS */
  
  /**
   * These constants allow mnemonic access to AnimateObject's final
   * constructor argument, i.e., should the object start running on
   * construction or on (a subsequent) call to a separate start()
   * method?
   *
   * @see #AnimateObject( boolean ) 
   */
  public static boolean START_IMMEDIATELY = true,
                        DONT_START_YET = false;

  /* FIELDS */

  /**
   * The animacy that makes this object go.
   *
   * @see cs101.lang.AnimatorThread
   */
  protected AnimatorThread spirit;
  

  /* CONSTRUCTORS */

  /**
   * The most basic constructor creates the AnimateObject and starts
   * its animacy going. 
   */
  public AnimateObject() 
  {
    this( AnimateObject.START_IMMEDIATELY );
  }
  
  /**
   * This constructor allows you to create an AnimateObject without
   * starting its animacy going. (You do this by calling this
   * constructor with <tt>AnimateObject.DONT_START_YET</tt>, i.e., the
   * boolean <tt>false</tt>. If you do this, the animacy will not
   * actually begin execution until you call this AnimateObject's
   * start() method.
   *
   * @param startImmediately   If false, execution does not start until
   *          explicit invocation of this object's start() method.
   *
   * @see #START_IMMEDIATELY
   * @see #DONT_START_YET
   */
  public AnimateObject( boolean startImmediately ) 
  {
    super();
    
    this.spirit = new AnimatorThread(this);
    if ( startImmediately )
      {
	this.spirit.startExecution();
      }
  }
  
  /**
   * Invocation of this method begins this object's autonomous execution.  
   *
   * (If execution has already begun, this method does nothing.)
   *
   * @see #AnimateObject( boolean )
   */
  public void start() {
    this.spirit.start();
  }

  /**
   * Override this method to give the AnimateObject behavior.
   *
   * The default behavior -- Thread.yield() -- simply gives other 
   * animacies a chance to run.
   */
  public abstract void act();
  
}

/* Comments:
 *
 * History:
 * $Log: AnimateObject.java,v $
 * Revision 1.1.1.1  2002/06/05 21:56:32  root
 * CS101 comes to Olin finally.
 *
 * Revision 1.4  1999/06/18 21:37:47  las
 * Updated AnimateObject to work with the new AnimatorThread/Animate
 * paradigm.  AnimateObject is now an abstract class; its act() method
 * must be overridden to create a useful object.
 *
 * Revision 1.3 1998/07/24 17:19:21 tparnell
 * Placate new javadoc behavior
 *
 * Revision 1.2 1998/06/24 20:58:36 tparnell
 * formatting fixed
 *
 * Revision 1.1 1998/06/08 18:11:52 tparnell
 * added files from Lynn
 *
 */