001package 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. 002 003import java.util.*; 004import votorola.g.lang.*; 005 006 007/** A null implementation of a spool. It is always empty and never unwinds. 008 */ 009public final @ThreadSafe class Spool0 extends AbstractCollection<Hold> implements Spool 010{ 011 012 private Spool0() {} 013 014 015 016 /** The single instance of Spool0. 017 */ 018 public static Spool0 i() { return instance; } 019 020 021 private static final Spool0 instance = new Spool0(); 022 023 024 025 // - C o l l e c t i o n -------------------------------------------------------------- 026 027 028 public Iterator<Hold> iterator() 029 { 030 List<Hold> emptyList = Collections.emptyList(); 031 return emptyList.iterator(); 032 } 033 034 035 036 /** Returns zero. 037 */ 038 public int size() { return 0; } 039 040 041 042 // - S p o o l ------------------------------------------------------------------------ 043 044 045 /** Does nothing and returns true. 046 */ 047 public boolean add( Hold hold ) { return true; } 048 049 050 051 /** Returns false. 052 */ 053 public boolean isUnwinding() { return false; } 054 055 056 057 /** Does nothing and returns false. 058 */ 059 public boolean unwind() { return false; } 060 061 062 063 /** Does nothing and returns false. 064 */ 065 public boolean unwind( Catcher<Hold> catcher ) { return false; } 066 067 068}