ant.java

一个TSP问题的图形演示程序

/*
 *  This code is from the book:
 *
 *    Winder, R and Roberts, G (2000) Developing Java
 *    Software, second edition, John Wiley & Sons.
 *
 *  It is copyright (c) 2000 Russel Winder and Graham Roberts.
 */

import SimFrameWork.Patch ;
import SimFrameWork.Turtle ;
import SimFrameWork.RandomGen ;
/**
 *  This class provides Ant objects for the simple ant foraging
 *  simulation, by specializing the Turtle class.
 *
 *  @version 2.0 March 1999
 *  @author Graham Roberts
 */
class Ant extends Turtle {
  /**
   *  Ant creation. An ant does not initially carry a wood chip.
   *
   *  @param p patch ant is initially located on.
   */
  Ant(Patch p) {
    super(p) ;
    chip = false ;
  }
  /**
   *  Update ant by one time step.
   */
  public void update() {
    // Move ant a random distance.
    move() ;
    // If ant has a chip and if the current patch already has
    // at least one chip on it then assume it is a pile and
    // drop chip.
    int val = location.value() ;
    if (chip && (val > 0)) {
      location.incrValue() ;
      chip = false ;
      return ;
    }
    // If the ant is not carrying anything and there is a chip
    // available pick it up.
    if (!chip && (val > 0)) {
      location.decrValue() ;
      chip = true ;
    }
  }
  /**
   *  Test if ant is carrying a wood chip.
   *
   *  @return return true if the ant is carrying a wood chip.
   */
  public boolean isLoaded() {
    return chip ;
  }
  /**
   *  Move ant a random distance in a random direction.
   */
  private void move() {
    int distance = RandomGen.getNext(3) ;
    int direction = RandomGen.getNext(8) ;
    Patch p = location ;
    for (int i = 0 ; i < distance ; ++i) {
      Patch t = p.getNeighbour(direction) ;
      if (t != null) {
        p = t ;
      }
    }
    location.removeTurtle(this) ;
    location = p ;
    location.addTurtle(this) ;
  }
  /**
   *  Set to true when ant is carrying a woodchip.
   */
  private boolean chip ;
}