package votorola.g.hold; // Copyright 2005-2006, Michael Allan.  Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Votorola Software"), to deal in the Votorola Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicence, and/or sell copies of the Votorola Software, and to permit persons to whom the Votorola Software is furnished to do so, subject to the following conditions: The preceding copyright notice and this permission notice shall be included in all copies or substantial portions of the Votorola Software. THE VOTOROLA SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE VOTOROLA SOFTWARE OR THE USE OR OTHER DEALINGS IN THE VOTOROLA SOFTWARE.

import java.util.*;
import votorola.g.lang.*;


/** A null implementation of a spool.  It is always empty and never unwinds.
  */
public final @ThreadSafe class Spool0 extends AbstractCollection<Hold> implements Spool
{

    private Spool0() {}



    /** The single instance of Spool0.
      */
    public static Spool0 i() { return instance; }


        private static final Spool0 instance = new Spool0();



   // - C o l l e c t i o n --------------------------------------------------------------


    public Iterator<Hold> iterator()
    {
        List<Hold> emptyList = Collections.emptyList();
        return emptyList.iterator();
    }



    /** Returns zero.
      */
    public int size() { return 0; }



   // - S p o o l ------------------------------------------------------------------------


    /** Does nothing and returns true.
      */
    public boolean add( Hold hold ) { return true; }



    /** Returns false.
      */
    public boolean isUnwinding() { return false; }



    /** Does nothing and returns false.
      */
    public boolean unwind() { return false; }



    /** Does nothing and returns false.
      */
    public boolean unwind( Catcher<Hold> catcher ) { return false; }


}