AbstractCollection


1   /*
2    * Copyright 2006 Google Inc.
3    * 
4    * Licensed under the Apache License, Version 2.0 (the "License"); you may not
5    * use this file except in compliance with the License. You may obtain a copy of
6    * the License at
7    * 
8    * http://www.apache.org/licenses/LICENSE-2.0
9    * 
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations under
14   * the License.
15   */
16  package java.util;
17  
18  /**
19   * Abstract base class for collection implementations.
20   */
21  public abstract class AbstractCollection implements Collection   {
22  
23    public boolean add(Object   o) {
24      throw new UnsupportedOperationException  ("add");
25    }
26  
27    public boolean addAll(Collection   c) {
28      Iterator   iter = c.iterator();
29      boolean changed = false;
30      while (iter.hasNext()) {
31        if (add(iter.next())) {
32          changed = true;
33        }
34      }
35      return changed;
36    }
37  
38    public void clear() {
39      Iterator   iter = iterator();
40      while (iter.hasNext()) {
41        iter.next();
42        iter.remove();
43      }
44    }
45  
46    public boolean contains(Object   o) {
47      Iterator   iter = advanceToFind(iterator(), o);
48      return iter == null ? false : true;
49    }
50  
51    public boolean containsAll(Collection   c) {
52      Iterator   iter = c.iterator();
53      while (iter.hasNext()) {
54        if (!contains(iter.next())) {
55          return false;
56        }
57      }
58      return true;
59    }
60  
61    public boolean isEmpty() {
62      return size() == 0;
63    }
64  
65    public abstract Iterator   iterator();
66  
67    public boolean remove(Object   o) {
68      Iterator   iter = advanceToFind(iterator(), o);
69      if (iter != null) {
70        iter.remove();
71        return true;
72      } else {
73        return false;
74      }
75    }
76  
77    public boolean removeAll(Collection   c) {
78      Iterator   iter = c.iterator();
79      boolean changed = false;
80      while (iter.hasNext()) {
81        if (remove(iter.next())) {
82          changed = true;
83        }
84      }
85      return changed;
86    }
87  
88    public boolean retainAll(Collection   c) {
89      Iterator   iter = iterator();
90      boolean changed = false;
91      while (iter.hasNext()) {
92        if (!c.contains(iter.next())) {
93          iter.remove();
94          changed = true;
95        }
96      }
97      return changed;
98    }
99  
100   public abstract int size();
101 
102   public Object  [] toArray() {
103     int n = size();
104     int i = 0;
105     Object  [] array = new Object  [n];
106     for (Iterator   iter = iterator(); iter.hasNext();) {
107       Object   o = iter.next();
108       array[i++] = o;
109     }
110     return array;
111   }
112 
113   public String   toString() {
114     StringBuffer   sb = new StringBuffer  ();
115     String   comma = null;
116     sb.append("[");
117     Iterator   iter = iterator();
118     while (iter.hasNext()) {
119       if (comma != null) {
120         sb.append(comma);
121       } else {
122         comma = ", ";
123       }
124       sb.append(String.valueOf(iter.next()));
125     }
126     sb.append("]");
127     return sb.toString();
128   }
129 
130   private Iterator   advanceToFind(Iterator   iter, Object   o) {
131     while (iter.hasNext()) {
132       Object   t = iter.next();
133       if (o == null ? t == null : o.equals(t)) {
134         return iter;
135       }
136     }
137     return null;
138   }
139 }
140
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