001 // Copyright 2004, 2005 The Apache Software Foundation 002 // 003 // Licensed under the Apache License, Version 2.0 (the "License"); 004 // you may not use this file except in compliance with the License. 005 // You may obtain a copy of the License at 006 // 007 // http://www.apache.org/licenses/LICENSE-2.0 008 // 009 // Unless required by applicable law or agreed to in writing, software 010 // distributed under the License is distributed on an "AS IS" BASIS, 011 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 012 // See the License for the specific language governing permissions and 013 // limitations under the License. 014 015 package org.apache.hivemind.impl; 016 017 import java.util.AbstractList; 018 import java.util.List; 019 020 /** 021 * Implements a {@link java.util.List} as a proxy to an actual list of 022 * elements, provided by an extension point. The proxy is unmodifiable 023 * and will work with the extension point to generate the real list 024 * of elements in a just-in-time manner. 025 * 026 * @author Howard Lewis Ship 027 */ 028 public final class ElementsInnerProxyList extends AbstractList 029 { 030 private List _inner; 031 private ConfigurationPointImpl _point; 032 private ElementsProxyList _outer; 033 034 ElementsInnerProxyList(ConfigurationPointImpl point, ElementsProxyList outer) 035 { 036 _point = point; 037 _outer = outer; 038 039 _outer.setInner(this); 040 } 041 042 private synchronized List inner() 043 { 044 if (_inner == null) 045 { 046 _inner = _point.constructElements(); 047 048 // Replace ourselves in the outer proxy with the actual list. 049 _outer.setInner(_inner); 050 } 051 052 return _inner; 053 } 054 055 public Object get(int index) 056 { 057 return inner().get(index); 058 } 059 060 public int size() 061 { 062 return inner().size(); 063 } 064 065 public boolean equals(Object o) 066 { 067 if (this == o) 068 return true; 069 070 if (o == null) 071 return false; 072 073 return inner().equals(o); 074 } 075 076 public int hashCode() 077 { 078 return inner().hashCode(); 079 } 080 081 public synchronized String toString() 082 { 083 if (_inner != null) 084 return _inner.toString(); 085 086 return "<Element List Proxy for " + _point.getExtensionPointId() + ">"; 087 } 088 089 }