control.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.
 */

package SimFrameWork ;
/**
 *  This class provides a basic extension of class Thread, providing a
 *  control loop and a safe way of terminating the thread.
 *
 *  @version 2.0 March 1999
 *  @author Graham Roberts
 */
public abstract class Control extends Thread {
  /**
   * Default constructor is declared for completeness but doesn't
   * do anything
   */
  public Control() {
  }
  /**
   *  Default run policy is to loop while the thread is kept active,
   *  and defer all other behaviour to an abstract update method.
   */
  public void run() {
    active = true ;
    while (active) {
      update() ;
    }
  }
  /**
   *  Stop the thread by setting the active flag to false.
   */
  public void stopControl() {
    active = false ;
  }
  /**
   *  Do whatever the thread does.
   */
  public abstract void update() ;
  /**
   *  Flag used to store active state of simulation thread.
   *  Declared as volatile as its value can be changed by a thread
   *  other than the simulation thread, and we want to guarantee that
   *  the simulation thread always reads its current value.
   */
  private volatile boolean active = false ;
}