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1   /*
2    * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved.
3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4    *
5    * This code is free software; you can redistribute it and/or modify it
6    * under the terms of the GNU General Public License version 2 only, as
7    * published by the Free Software Foundation.  Oracle designates this
8    * particular file as subject to the "Classpath" exception as provided
9    * by Oracle in the LICENSE file that accompanied this code.
10   *
11   * This code is distributed in the hope that it will be useful, but WITHOUT
12   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14   * version 2 for more details (a copy is included in the LICENSE file that
15   * accompanied this code).
16   *
17   * You should have received a copy of the GNU General Public License version
18   * 2 along with this work; if not, write to the Free Software Foundation,
19   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20   *
21   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22   * or visit www.oracle.com if you need additional information or have any
23   * questions.
24   */
25  
26  package com.sun.xml.internal.xsom.util;
27  
28  import java.util.ArrayList;
29  import java.util.Collection;
30  import java.util.Iterator;
31  import java.util.List;
32  import java.util.NoSuchElementException;
33  
34  /**
35   * {@link Collection} that returns the view of objects which are actually fetched
36   * lazily from an {@link Iterator}.
37   *
38   * @author Kohsuke Kawaguchi
39   */
40  public class DeferedCollection<T> implements Collection<T> {
41      /**
42       * The iterator that lazily evaluates SCD query.
43       */
44      private final Iterator<T> result;
45  
46      /**
47       * Stores values that are already fetched from {@link #result}.
48       */
49      private final List<T> archive = new ArrayList<T>();
50  
51      public DeferedCollection(Iterator<T> result) {
52          this.result = result;
53      }
54  
55      public boolean isEmpty() {
56          if(archive.isEmpty())
57              fetch();
58          return archive.isEmpty();
59      }
60  
61      public int size() {
62          fetchAll();
63          return archive.size();
64      }
65  
66      public boolean contains(Object o) {
67          if(archive.contains(o))
68              return true;
69          while(result.hasNext()) {
70              T value = result.next();
71              archive.add(value);
72              if(value.equals(o))
73                  return true;
74          }
75          return false;
76      }
77  
78      public boolean containsAll(Collection<?> c) {
79          for (Object o : c) {
80              if(!contains(o))
81                  return false;
82          }
83          return true;
84      }
85  
86      public Iterator<T> iterator() {
87          return new Iterator<T>() {
88              int idx=0;
89              public boolean hasNext() {
90                  if(idx<archive.size())
91                      return true;
92                  return result.hasNext();
93              }
94  
95              public T next() {
96                  if(idx==archive.size())
97                      fetch();
98                  if(idx==archive.size())
99                      throw new NoSuchElementException();
100                 return archive.get(idx++);
101             }
102 
103             public void remove() {
104                 // TODO
105             }
106         };
107     }
108 
109     public Object[] toArray() {
110         fetchAll();
111         return archive.toArray();
112     }
113 
114     public <T>T[] toArray(T[] a) {
115         fetchAll();
116         return archive.toArray(a);
117     }
118 
119 
120 
121     private void fetchAll() {
122         while(result.hasNext())
123             archive.add(result.next());
124     }
125 
126     /**
127      * Fetches another item from {@link
128      */
129     private void fetch() {
130         if(result.hasNext())
131             archive.add(result.next());
132     }
133 
134 // mutation methods are unsupported
135     public boolean add(T o) {
136         throw new UnsupportedOperationException();
137     }
138 
139     public boolean remove(Object o) {
140         throw new UnsupportedOperationException();
141     }
142 
143     public boolean addAll(Collection<? extends T> c) {
144         throw new UnsupportedOperationException();
145     }
146 
147     public boolean removeAll(Collection<?> c) {
148         throw new UnsupportedOperationException();
149     }
150 
151     public boolean retainAll(Collection<?> c) {
152         throw new UnsupportedOperationException();
153     }
154 
155     public void clear() {
156         throw new UnsupportedOperationException();
157     }
158 }