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dl |
1.1 |
/* |
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jsr166 |
1.3 |
* %W% %E% |
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1.1 |
* |
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jsr166 |
1.5 |
* Copyright 2006 Sun Microsystems, Inc. All rights reserved. |
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1.1 |
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
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*/ |
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package java.util; |
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/** |
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* This class provides a skeletal implementation of the <tt>Collection</tt> |
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* interface, to minimize the effort required to implement this interface. <p> |
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* |
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* To implement an unmodifiable collection, the programmer needs only to |
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* extend this class and provide implementations for the <tt>iterator</tt> and |
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* <tt>size</tt> methods. (The iterator returned by the <tt>iterator</tt> |
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* method must implement <tt>hasNext</tt> and <tt>next</tt>.)<p> |
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* |
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* To implement a modifiable collection, the programmer must additionally |
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* override this class's <tt>add</tt> method (which otherwise throws an |
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* <tt>UnsupportedOperationException</tt>), and the iterator returned by the |
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* <tt>iterator</tt> method must additionally implement its <tt>remove</tt> |
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* method.<p> |
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* |
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* The programmer should generally provide a void (no argument) and |
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* <tt>Collection</tt> constructor, as per the recommendation in the |
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* <tt>Collection</tt> interface specification.<p> |
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* |
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jsr166 |
1.9 |
* The documentation for each non-abstract method in this class describes its |
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1.1 |
* implementation in detail. Each of these methods may be overridden if |
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* the collection being implemented admits a more efficient implementation.<p> |
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* |
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* This class is a member of the |
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jsr166 |
1.8 |
* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
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1.1 |
* Java Collections Framework</a>. |
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* |
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* @author Josh Bloch |
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* @author Neal Gafter |
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jsr166 |
1.6 |
* @version %I%, %G% |
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1.1 |
* @see Collection |
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* @since 1.2 |
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*/ |
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public abstract class AbstractCollection<E> implements Collection<E> { |
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/** |
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* Sole constructor. (For invocation by subclass constructors, typically |
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* implicit.) |
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*/ |
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protected AbstractCollection() { |
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} |
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// Query Operations |
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/** |
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* Returns an iterator over the elements contained in this collection. |
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* |
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* @return an iterator over the elements contained in this collection |
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*/ |
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public abstract Iterator<E> iterator(); |
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public abstract int size(); |
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/** |
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* {@inheritDoc} |
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* |
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* <p>This implementation returns <tt>size() == 0</tt>. |
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*/ |
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public boolean isEmpty() { |
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return size() == 0; |
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} |
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/** |
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* {@inheritDoc} |
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* |
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* <p>This implementation iterates over the elements in the collection, |
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* checking each element in turn for equality with the specified element. |
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* |
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* @throws ClassCastException {@inheritDoc} |
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* @throws NullPointerException {@inheritDoc} |
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*/ |
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public boolean contains(Object o) { |
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Iterator<E> e = iterator(); |
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if (o==null) { |
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while (e.hasNext()) |
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if (e.next()==null) |
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return true; |
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} else { |
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while (e.hasNext()) |
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if (o.equals(e.next())) |
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return true; |
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} |
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return false; |
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} |
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/** |
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* {@inheritDoc} |
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* |
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1.9 |
* <p>This implementation returns an array containing all the elements |
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* returned by this collection's iterator, in the same order, stored in |
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* consecutive elements of the array, starting with index {@code 0}. |
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* The length of the returned array is equal to the number of elements |
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* returned by the iterator, even if the size of this collection changes |
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* during iteration, as might happen if the collection permits |
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* concurrent modification during iteration. The {@code size} method is |
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* called only as an optimization hint; the correct result is returned |
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* even if the iterator returns a different number of elements. |
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* |
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* <p>This method is equivalent to: |
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* |
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* <pre> {@code |
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* List<E> list = new ArrayList<E>(size()); |
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* for (E e : this) |
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* list.add(e); |
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* return list.toArray(); |
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* }</pre> |
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1.1 |
*/ |
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public Object[] toArray() { |
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// Estimate size of array; be prepared to see more or fewer elements |
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Object[] r = new Object[size()]; |
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jsr166 |
1.3 |
Iterator<E> it = iterator(); |
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jsr166 |
1.9 |
for (int i = 0; i < r.length; i++) { |
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if (! it.hasNext()) // fewer elements than expected |
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return Arrays.copyOf(r, i); |
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r[i] = it.next(); |
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} |
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return it.hasNext() ? finishToArray(r, it) : r; |
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1.1 |
} |
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/** |
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* {@inheritDoc} |
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* |
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jsr166 |
1.9 |
* <p>This implementation returns an array containing all the elements |
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* returned by this collection's iterator in the same order, stored in |
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* consecutive elements of the array, starting with index {@code 0}. |
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* If the number of elements returned by the iterator is too large to |
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* fit into the specified array, then the elements are returned in a |
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* newly allocated array with length equal to the number of elements |
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* returned by the iterator, even if the size of this collection |
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* changes during iteration, as might happen if the collection permits |
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* concurrent modification during iteration. The {@code size} method is |
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* called only as an optimization hint; the correct result is returned |
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* even if the iterator returns a different number of elements. |
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* |
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* <p>This method is equivalent to: |
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* |
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* <pre> {@code |
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* List<E> list = new ArrayList<E>(size()); |
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* for (E e : this) |
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* list.add(e); |
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* return list.toArray(a); |
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* }</pre> |
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dl |
1.1 |
* |
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* @throws ArrayStoreException {@inheritDoc} |
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* @throws NullPointerException {@inheritDoc} |
155 |
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*/ |
156 |
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public <T> T[] toArray(T[] a) { |
157 |
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// Estimate size of array; be prepared to see more or fewer elements |
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int size = size(); |
159 |
jsr166 |
1.3 |
T[] r = a.length >= size ? a : |
160 |
dl |
1.1 |
(T[])java.lang.reflect.Array |
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.newInstance(a.getClass().getComponentType(), size); |
162 |
jsr166 |
1.3 |
Iterator<E> it = iterator(); |
163 |
jsr166 |
1.9 |
|
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for (int i = 0; i < r.length; i++) { |
165 |
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if (! it.hasNext()) { // fewer elements than expected |
166 |
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if (a != r) |
167 |
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return Arrays.copyOf(r, i); |
168 |
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r[i] = null; // null-terminate |
169 |
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return r; |
170 |
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} |
171 |
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r[i] = (T)it.next(); |
172 |
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} |
173 |
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return it.hasNext() ? finishToArray(r, it) : r; |
174 |
dl |
1.1 |
} |
175 |
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176 |
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/** |
177 |
jsr166 |
1.9 |
* Reallocates the array being used within toArray when the iterator |
178 |
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* returned more elements than expected, and finishes filling it from |
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* the iterator. |
180 |
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* |
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* @param r the array, replete with previously stored elements |
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* @param it the in-progress iterator over this collection |
183 |
jsr166 |
1.3 |
* @return array containing the elements in the given array, plus any |
184 |
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* further elements returned by the iterator, trimmed to size |
185 |
dl |
1.1 |
*/ |
186 |
jsr166 |
1.9 |
private static <T> T[] finishToArray(T[] r, Iterator<?> it) { |
187 |
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int i = r.length; |
188 |
jsr166 |
1.2 |
while (it.hasNext()) { |
189 |
dl |
1.1 |
int cap = r.length; |
190 |
jsr166 |
1.9 |
if (i == cap) { |
191 |
dl |
1.4 |
int newCap = ((cap / 2) + 1) * 3; |
192 |
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if (newCap <= cap) { // integer overflow |
193 |
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if (cap == Integer.MAX_VALUE) |
194 |
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throw new OutOfMemoryError |
195 |
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("Required array size too large"); |
196 |
jsr166 |
1.9 |
newCap = Integer.MAX_VALUE; |
197 |
dl |
1.4 |
} |
198 |
jsr166 |
1.9 |
r = Arrays.copyOf(r, newCap); |
199 |
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} |
200 |
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r[i++] = (T)it.next(); |
201 |
jsr166 |
1.7 |
} |
202 |
dl |
1.1 |
// trim if overallocated |
203 |
jsr166 |
1.9 |
return (i == r.length) ? r : Arrays.copyOf(r, i); |
204 |
dl |
1.1 |
} |
205 |
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206 |
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// Modification Operations |
207 |
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208 |
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/** |
209 |
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* {@inheritDoc} |
210 |
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* |
211 |
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* <p>This implementation always throws an |
212 |
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* <tt>UnsupportedOperationException</tt>. |
213 |
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* |
214 |
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* @throws UnsupportedOperationException {@inheritDoc} |
215 |
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* @throws ClassCastException {@inheritDoc} |
216 |
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* @throws NullPointerException {@inheritDoc} |
217 |
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* @throws IllegalArgumentException {@inheritDoc} |
218 |
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* @throws IllegalStateException {@inheritDoc} |
219 |
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*/ |
220 |
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public boolean add(E e) { |
221 |
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throw new UnsupportedOperationException(); |
222 |
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} |
223 |
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224 |
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/** |
225 |
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* {@inheritDoc} |
226 |
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* |
227 |
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* <p>This implementation iterates over the collection looking for the |
228 |
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* specified element. If it finds the element, it removes the element |
229 |
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* from the collection using the iterator's remove method. |
230 |
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* |
231 |
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* <p>Note that this implementation throws an |
232 |
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* <tt>UnsupportedOperationException</tt> if the iterator returned by this |
233 |
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* collection's iterator method does not implement the <tt>remove</tt> |
234 |
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* method and this collection contains the specified object. |
235 |
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* |
236 |
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* @throws UnsupportedOperationException {@inheritDoc} |
237 |
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* @throws ClassCastException {@inheritDoc} |
238 |
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* @throws NullPointerException {@inheritDoc} |
239 |
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*/ |
240 |
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public boolean remove(Object o) { |
241 |
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Iterator<E> e = iterator(); |
242 |
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if (o==null) { |
243 |
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while (e.hasNext()) { |
244 |
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if (e.next()==null) { |
245 |
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e.remove(); |
246 |
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return true; |
247 |
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} |
248 |
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} |
249 |
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} else { |
250 |
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while (e.hasNext()) { |
251 |
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if (o.equals(e.next())) { |
252 |
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e.remove(); |
253 |
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return true; |
254 |
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} |
255 |
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} |
256 |
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} |
257 |
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return false; |
258 |
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} |
259 |
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260 |
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261 |
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// Bulk Operations |
262 |
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263 |
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/** |
264 |
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* {@inheritDoc} |
265 |
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* |
266 |
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* <p>This implementation iterates over the specified collection, |
267 |
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* checking each element returned by the iterator in turn to see |
268 |
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* if it's contained in this collection. If all elements are so |
269 |
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* contained <tt>true</tt> is returned, otherwise <tt>false</tt>. |
270 |
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* |
271 |
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* @throws ClassCastException {@inheritDoc} |
272 |
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* @throws NullPointerException {@inheritDoc} |
273 |
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* @see #contains(Object) |
274 |
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*/ |
275 |
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public boolean containsAll(Collection<?> c) { |
276 |
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Iterator<?> e = c.iterator(); |
277 |
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while (e.hasNext()) |
278 |
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if (!contains(e.next())) |
279 |
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return false; |
280 |
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return true; |
281 |
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} |
282 |
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283 |
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/** |
284 |
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* {@inheritDoc} |
285 |
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* |
286 |
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* <p>This implementation iterates over the specified collection, and adds |
287 |
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* each object returned by the iterator to this collection, in turn. |
288 |
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* |
289 |
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* <p>Note that this implementation will throw an |
290 |
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* <tt>UnsupportedOperationException</tt> unless <tt>add</tt> is |
291 |
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* overridden (assuming the specified collection is non-empty). |
292 |
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* |
293 |
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* @throws UnsupportedOperationException {@inheritDoc} |
294 |
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* @throws ClassCastException {@inheritDoc} |
295 |
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* @throws NullPointerException {@inheritDoc} |
296 |
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* @throws IllegalArgumentException {@inheritDoc} |
297 |
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* @throws IllegalStateException {@inheritDoc} |
298 |
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* |
299 |
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* @see #add(Object) |
300 |
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*/ |
301 |
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public boolean addAll(Collection<? extends E> c) { |
302 |
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boolean modified = false; |
303 |
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Iterator<? extends E> e = c.iterator(); |
304 |
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while (e.hasNext()) { |
305 |
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if (add(e.next())) |
306 |
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modified = true; |
307 |
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} |
308 |
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return modified; |
309 |
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} |
310 |
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311 |
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/** |
312 |
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* {@inheritDoc} |
313 |
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* |
314 |
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* <p>This implementation iterates over this collection, checking each |
315 |
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* element returned by the iterator in turn to see if it's contained |
316 |
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* in the specified collection. If it's so contained, it's removed from |
317 |
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* this collection with the iterator's <tt>remove</tt> method. |
318 |
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* |
319 |
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* <p>Note that this implementation will throw an |
320 |
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* <tt>UnsupportedOperationException</tt> if the iterator returned by the |
321 |
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* <tt>iterator</tt> method does not implement the <tt>remove</tt> method |
322 |
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* and this collection contains one or more elements in common with the |
323 |
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* specified collection. |
324 |
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* |
325 |
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* @throws UnsupportedOperationException {@inheritDoc} |
326 |
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* @throws ClassCastException {@inheritDoc} |
327 |
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* @throws NullPointerException {@inheritDoc} |
328 |
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* |
329 |
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* @see #remove(Object) |
330 |
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* @see #contains(Object) |
331 |
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*/ |
332 |
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public boolean removeAll(Collection<?> c) { |
333 |
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boolean modified = false; |
334 |
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Iterator<?> e = iterator(); |
335 |
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while (e.hasNext()) { |
336 |
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if (c.contains(e.next())) { |
337 |
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e.remove(); |
338 |
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modified = true; |
339 |
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} |
340 |
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} |
341 |
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return modified; |
342 |
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} |
343 |
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344 |
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/** |
345 |
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* {@inheritDoc} |
346 |
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* |
347 |
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* <p>This implementation iterates over this collection, checking each |
348 |
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* element returned by the iterator in turn to see if it's contained |
349 |
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* in the specified collection. If it's not so contained, it's removed |
350 |
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* from this collection with the iterator's <tt>remove</tt> method. |
351 |
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* |
352 |
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* <p>Note that this implementation will throw an |
353 |
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* <tt>UnsupportedOperationException</tt> if the iterator returned by the |
354 |
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* <tt>iterator</tt> method does not implement the <tt>remove</tt> method |
355 |
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* and this collection contains one or more elements not present in the |
356 |
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* specified collection. |
357 |
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* |
358 |
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* @throws UnsupportedOperationException {@inheritDoc} |
359 |
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* @throws ClassCastException {@inheritDoc} |
360 |
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* @throws NullPointerException {@inheritDoc} |
361 |
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* |
362 |
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* @see #remove(Object) |
363 |
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* @see #contains(Object) |
364 |
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*/ |
365 |
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public boolean retainAll(Collection<?> c) { |
366 |
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boolean modified = false; |
367 |
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Iterator<E> e = iterator(); |
368 |
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while (e.hasNext()) { |
369 |
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if (!c.contains(e.next())) { |
370 |
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e.remove(); |
371 |
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modified = true; |
372 |
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} |
373 |
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} |
374 |
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return modified; |
375 |
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} |
376 |
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|
377 |
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/** |
378 |
|
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* {@inheritDoc} |
379 |
|
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* |
380 |
|
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* <p>This implementation iterates over this collection, removing each |
381 |
|
|
* element using the <tt>Iterator.remove</tt> operation. Most |
382 |
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* implementations will probably choose to override this method for |
383 |
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* efficiency. |
384 |
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* |
385 |
|
|
* <p>Note that this implementation will throw an |
386 |
|
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* <tt>UnsupportedOperationException</tt> if the iterator returned by this |
387 |
|
|
* collection's <tt>iterator</tt> method does not implement the |
388 |
|
|
* <tt>remove</tt> method and this collection is non-empty. |
389 |
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* |
390 |
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* @throws UnsupportedOperationException {@inheritDoc} |
391 |
|
|
*/ |
392 |
|
|
public void clear() { |
393 |
|
|
Iterator<E> e = iterator(); |
394 |
|
|
while (e.hasNext()) { |
395 |
|
|
e.next(); |
396 |
|
|
e.remove(); |
397 |
|
|
} |
398 |
|
|
} |
399 |
|
|
|
400 |
|
|
|
401 |
|
|
// String conversion |
402 |
|
|
|
403 |
|
|
/** |
404 |
|
|
* Returns a string representation of this collection. The string |
405 |
|
|
* representation consists of a list of the collection's elements in the |
406 |
|
|
* order they are returned by its iterator, enclosed in square brackets |
407 |
|
|
* (<tt>"[]"</tt>). Adjacent elements are separated by the characters |
408 |
|
|
* <tt>", "</tt> (comma and space). Elements are converted to strings as |
409 |
|
|
* by {@link String#valueOf(Object)}. |
410 |
|
|
* |
411 |
|
|
* @return a string representation of this collection |
412 |
|
|
*/ |
413 |
|
|
public String toString() { |
414 |
|
|
Iterator<E> i = iterator(); |
415 |
|
|
if (! i.hasNext()) |
416 |
|
|
return "[]"; |
417 |
|
|
|
418 |
|
|
StringBuilder sb = new StringBuilder(); |
419 |
|
|
sb.append('['); |
420 |
|
|
for (;;) { |
421 |
|
|
E e = i.next(); |
422 |
|
|
sb.append(e == this ? "(this Collection)" : e); |
423 |
|
|
if (! i.hasNext()) |
424 |
|
|
return sb.append(']').toString(); |
425 |
|
|
sb.append(", "); |
426 |
|
|
} |
427 |
|
|
} |
428 |
|
|
|
429 |
|
|
} |