abstractpositionalcontainer.java

Java数据结构开发包

/*
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*/

package jdsl.core.ref;

import jdsl.core.api.*;



/**
 * An abstract positional container that others may extend if they do not
 * wish to deal with some of the more mundane aspects of 
 * positional containers and/or if they wish to avoid implementing themselves
 * some of the methods of container that aren't terribly pertinent to
 * a PositionalContainer.  Feel free to override any of these methods in
 * subclasses, but be certain that they work according
 * to the API in jdsl.core.api.
 *
 * Also handles isEmpty() from InspectableContainer.
 *
 * @version JDSL 2.1.1 
 * @author Andrew Schwerin (schwerin)
 * @author Benoit Hudson (bh)
 * @author Ryan Shaun Baker (rsb)
 * @see PositionalContainer
 */
public abstract class AbstractPositionalContainer
  implements PositionalContainer {

  /** 
   * Works on top of PositionalContainer method
   * replaceElement(Position, Object) and InspectableContainer method
   * contains().  
   */
  public void swapElements(Position a, Position b)
    throws InvalidAccessorException {

    // Require that both of the swappees be in this container
    if((!this.contains(a)) || (!this.contains(b)))
      throw new InvalidAccessorException
	("Positions do not belong to this container");
    
    Object aelt = a.element();
    replaceElement(a,b.element());
    replaceElement(b,aelt);
    
    }

  
  /** 
   * Checks if this container is empty. 
   * Has the same time complexity as size().  If size() is O(n) and you can
   * write isEmpty() in O(1) time, then override this method.
   */
  public boolean isEmpty() { return (size() == 0); }
    
}