| /* |
| * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package java.util; |
| |
| /** |
| * This class provides a skeletal implementation of the <tt>Collection</tt> |
| * interface, to minimize the effort required to implement this interface. <p> |
| * |
| * To implement an unmodifiable collection, the programmer needs only to |
| * extend this class and provide implementations for the <tt>iterator</tt> and |
| * <tt>size</tt> methods. (The iterator returned by the <tt>iterator</tt> |
| * method must implement <tt>hasNext</tt> and <tt>next</tt>.)<p> |
| * |
| * To implement a modifiable collection, the programmer must additionally |
| * override this class's <tt>add</tt> method (which otherwise throws an |
| * <tt>UnsupportedOperationException</tt>), and the iterator returned by the |
| * <tt>iterator</tt> method must additionally implement its <tt>remove</tt> |
| * method.<p> |
| * |
| * The programmer should generally provide a void (no argument) and |
| * <tt>Collection</tt> constructor, as per the recommendation in the |
| * <tt>Collection</tt> interface specification.<p> |
| * |
| * The documentation for each non-abstract method in this class describes its |
| * implementation in detail. Each of these methods may be overridden if |
| * the collection being implemented admits a more efficient implementation.<p> |
| * |
| * This class is a member of the |
| * <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
| * Java Collections Framework</a>. |
| * |
| * @author Josh Bloch |
| * @author Neal Gafter |
| * @see Collection |
| * @since 1.2 |
| */ |
| |
| public abstract class AbstractCollection<E> implements Collection<E> { |
| /** |
| * Sole constructor. (For invocation by subclass constructors, typically |
| * implicit.) |
| */ |
| protected AbstractCollection() { |
| } |
| |
| // Query Operations |
| |
| /** |
| * Returns an iterator over the elements contained in this collection. |
| * |
| * @return an iterator over the elements contained in this collection |
| */ |
| public abstract Iterator<E> iterator(); |
| |
| public abstract int size(); |
| |
| /** |
| * {@inheritDoc} |
| * |
| * <p>This implementation returns <tt>size() == 0</tt>. |
| */ |
| public boolean isEmpty() { |
| return size() == 0; |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * <p>This implementation iterates over the elements in the collection, |
| * checking each element in turn for equality with the specified element. |
| * |
| * @throws ClassCastException {@inheritDoc} |
| * @throws NullPointerException {@inheritDoc} |
| */ |
| public boolean contains(Object o) { |
| Iterator<E> it = iterator(); |
| if (o==null) { |
| while (it.hasNext()) |
| if (it.next()==null) |
| return true; |
| } else { |
| while (it.hasNext()) |
| if (o.equals(it.next())) |
| return true; |
| } |
| return false; |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * <p>This implementation returns an array containing all the elements |
| * returned by this collection's iterator, in the same order, stored in |
| * consecutive elements of the array, starting with index {@code 0}. |
| * The length of the returned array is equal to the number of elements |
| * returned by the iterator, even if the size of this collection changes |
| * during iteration, as might happen if the collection permits |
| * concurrent modification during iteration. The {@code size} method is |
| * called only as an optimization hint; the correct result is returned |
| * even if the iterator returns a different number of elements. |
| * |
| * <p>This method is equivalent to: |
| * |
| * <pre> {@code |
| * List<E> list = new ArrayList<E>(size()); |
| * for (E e : this) |
| * list.add(e); |
| * return list.toArray(); |
| * }</pre> |
| */ |
| public Object[] toArray() { |
| // Estimate size of array; be prepared to see more or fewer elements |
| Object[] r = new Object[size()]; |
| Iterator<E> it = iterator(); |
| for (int i = 0; i < r.length; i++) { |
| if (! it.hasNext()) // fewer elements than expected |
| return Arrays.copyOf(r, i); |
| r[i] = it.next(); |
| } |
| return it.hasNext() ? finishToArray(r, it) : r; |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * <p>This implementation returns an array containing all the elements |
| * returned by this collection's iterator in the same order, stored in |
| * consecutive elements of the array, starting with index {@code 0}. |
| * If the number of elements returned by the iterator is too large to |
| * fit into the specified array, then the elements are returned in a |
| * newly allocated array with length equal to the number of elements |
| * returned by the iterator, even if the size of this collection |
| * changes during iteration, as might happen if the collection permits |
| * concurrent modification during iteration. The {@code size} method is |
| * called only as an optimization hint; the correct result is returned |
| * even if the iterator returns a different number of elements. |
| * |
| * <p>This method is equivalent to: |
| * |
| * <pre> {@code |
| * List<E> list = new ArrayList<E>(size()); |
| * for (E e : this) |
| * list.add(e); |
| * return list.toArray(a); |
| * }</pre> |
| * |
| * @throws ArrayStoreException {@inheritDoc} |
| * @throws NullPointerException {@inheritDoc} |
| */ |
| @SuppressWarnings("unchecked") |
| public <T> T[] toArray(T[] a) { |
| // Estimate size of array; be prepared to see more or fewer elements |
| int size = size(); |
| T[] r = a.length >= size ? a : |
| (T[])java.lang.reflect.Array |
| .newInstance(a.getClass().getComponentType(), size); |
| Iterator<E> it = iterator(); |
| |
| for (int i = 0; i < r.length; i++) { |
| if (! it.hasNext()) { // fewer elements than expected |
| if (a == r) { |
| r[i] = null; // null-terminate |
| } else if (a.length < i) { |
| return Arrays.copyOf(r, i); |
| } else { |
| System.arraycopy(r, 0, a, 0, i); |
| if (a.length > i) { |
| a[i] = null; |
| } |
| } |
| return a; |
| } |
| r[i] = (T)it.next(); |
| } |
| // more elements than expected |
| return it.hasNext() ? finishToArray(r, it) : r; |
| } |
| |
| /** |
| * The maximum size of array to allocate. |
| * Some VMs reserve some header words in an array. |
| * Attempts to allocate larger arrays may result in |
| * OutOfMemoryError: Requested array size exceeds VM limit |
| */ |
| private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; |
| |
| /** |
| * Reallocates the array being used within toArray when the iterator |
| * returned more elements than expected, and finishes filling it from |
| * the iterator. |
| * |
| * @param r the array, replete with previously stored elements |
| * @param it the in-progress iterator over this collection |
| * @return array containing the elements in the given array, plus any |
| * further elements returned by the iterator, trimmed to size |
| */ |
| @SuppressWarnings("unchecked") |
| private static <T> T[] finishToArray(T[] r, Iterator<?> it) { |
| int i = r.length; |
| while (it.hasNext()) { |
| int cap = r.length; |
| if (i == cap) { |
| int newCap = cap + (cap >> 1) + 1; |
| // overflow-conscious code |
| if (newCap - MAX_ARRAY_SIZE > 0) |
| newCap = hugeCapacity(cap + 1); |
| r = Arrays.copyOf(r, newCap); |
| } |
| r[i++] = (T)it.next(); |
| } |
| // trim if overallocated |
| return (i == r.length) ? r : Arrays.copyOf(r, i); |
| } |
| |
| private static int hugeCapacity(int minCapacity) { |
| if (minCapacity < 0) // overflow |
| throw new OutOfMemoryError |
| ("Required array size too large"); |
| return (minCapacity > MAX_ARRAY_SIZE) ? |
| Integer.MAX_VALUE : |
| MAX_ARRAY_SIZE; |
| } |
| |
| // Modification Operations |
| |
| /** |
| * {@inheritDoc} |
| * |
| * <p>This implementation always throws an |
| * <tt>UnsupportedOperationException</tt>. |
| * |
| * @throws UnsupportedOperationException {@inheritDoc} |
| * @throws ClassCastException {@inheritDoc} |
| * @throws NullPointerException {@inheritDoc} |
| * @throws IllegalArgumentException {@inheritDoc} |
| * @throws IllegalStateException {@inheritDoc} |
| */ |
| public boolean add(E e) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * <p>This implementation iterates over the collection looking for the |
| * specified element. If it finds the element, it removes the element |
| * from the collection using the iterator's remove method. |
| * |
| * <p>Note that this implementation throws an |
| * <tt>UnsupportedOperationException</tt> if the iterator returned by this |
| * collection's iterator method does not implement the <tt>remove</tt> |
| * method and this collection contains the specified object. |
| * |
| * @throws UnsupportedOperationException {@inheritDoc} |
| * @throws ClassCastException {@inheritDoc} |
| * @throws NullPointerException {@inheritDoc} |
| */ |
| public boolean remove(Object o) { |
| Iterator<E> it = iterator(); |
| if (o==null) { |
| while (it.hasNext()) { |
| if (it.next()==null) { |
| it.remove(); |
| return true; |
| } |
| } |
| } else { |
| while (it.hasNext()) { |
| if (o.equals(it.next())) { |
| it.remove(); |
| return true; |
| } |
| } |
| } |
| return false; |
| } |
| |
| |
| // Bulk Operations |
| |
| /** |
| * {@inheritDoc} |
| * |
| * <p>This implementation iterates over the specified collection, |
| * checking each element returned by the iterator in turn to see |
| * if it's contained in this collection. If all elements are so |
| * contained <tt>true</tt> is returned, otherwise <tt>false</tt>. |
| * |
| * @throws ClassCastException {@inheritDoc} |
| * @throws NullPointerException {@inheritDoc} |
| * @see #contains(Object) |
| */ |
| public boolean containsAll(Collection<?> c) { |
| for (Object e : c) |
| if (!contains(e)) |
| return false; |
| return true; |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * <p>This implementation iterates over the specified collection, and adds |
| * each object returned by the iterator to this collection, in turn. |
| * |
| * <p>Note that this implementation will throw an |
| * <tt>UnsupportedOperationException</tt> unless <tt>add</tt> is |
| * overridden (assuming the specified collection is non-empty). |
| * |
| * @throws UnsupportedOperationException {@inheritDoc} |
| * @throws ClassCastException {@inheritDoc} |
| * @throws NullPointerException {@inheritDoc} |
| * @throws IllegalArgumentException {@inheritDoc} |
| * @throws IllegalStateException {@inheritDoc} |
| * |
| * @see #add(Object) |
| */ |
| public boolean addAll(Collection<? extends E> c) { |
| boolean modified = false; |
| for (E e : c) |
| if (add(e)) |
| modified = true; |
| return modified; |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * <p>This implementation iterates over this collection, checking each |
| * element returned by the iterator in turn to see if it's contained |
| * in the specified collection. If it's so contained, it's removed from |
| * this collection with the iterator's <tt>remove</tt> method. |
| * |
| * <p>Note that this implementation will throw an |
| * <tt>UnsupportedOperationException</tt> if the iterator returned by the |
| * <tt>iterator</tt> method does not implement the <tt>remove</tt> method |
| * and this collection contains one or more elements in common with the |
| * specified collection. |
| * |
| * @throws UnsupportedOperationException {@inheritDoc} |
| * @throws ClassCastException {@inheritDoc} |
| * @throws NullPointerException {@inheritDoc} |
| * |
| * @see #remove(Object) |
| * @see #contains(Object) |
| */ |
| public boolean removeAll(Collection<?> c) { |
| Objects.requireNonNull(c); |
| boolean modified = false; |
| Iterator<?> it = iterator(); |
| while (it.hasNext()) { |
| if (c.contains(it.next())) { |
| it.remove(); |
| modified = true; |
| } |
| } |
| return modified; |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * <p>This implementation iterates over this collection, checking each |
| * element returned by the iterator in turn to see if it's contained |
| * in the specified collection. If it's not so contained, it's removed |
| * from this collection with the iterator's <tt>remove</tt> method. |
| * |
| * <p>Note that this implementation will throw an |
| * <tt>UnsupportedOperationException</tt> if the iterator returned by the |
| * <tt>iterator</tt> method does not implement the <tt>remove</tt> method |
| * and this collection contains one or more elements not present in the |
| * specified collection. |
| * |
| * @throws UnsupportedOperationException {@inheritDoc} |
| * @throws ClassCastException {@inheritDoc} |
| * @throws NullPointerException {@inheritDoc} |
| * |
| * @see #remove(Object) |
| * @see #contains(Object) |
| */ |
| public boolean retainAll(Collection<?> c) { |
| Objects.requireNonNull(c); |
| boolean modified = false; |
| Iterator<E> it = iterator(); |
| while (it.hasNext()) { |
| if (!c.contains(it.next())) { |
| it.remove(); |
| modified = true; |
| } |
| } |
| return modified; |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * <p>This implementation iterates over this collection, removing each |
| * element using the <tt>Iterator.remove</tt> operation. Most |
| * implementations will probably choose to override this method for |
| * efficiency. |
| * |
| * <p>Note that this implementation will throw an |
| * <tt>UnsupportedOperationException</tt> if the iterator returned by this |
| * collection's <tt>iterator</tt> method does not implement the |
| * <tt>remove</tt> method and this collection is non-empty. |
| * |
| * @throws UnsupportedOperationException {@inheritDoc} |
| */ |
| public void clear() { |
| Iterator<E> it = iterator(); |
| while (it.hasNext()) { |
| it.next(); |
| it.remove(); |
| } |
| } |
| |
| |
| // String conversion |
| |
| /** |
| * Returns a string representation of this collection. The string |
| * representation consists of a list of the collection's elements in the |
| * order they are returned by its iterator, enclosed in square brackets |
| * (<tt>"[]"</tt>). Adjacent elements are separated by the characters |
| * <tt>", "</tt> (comma and space). Elements are converted to strings as |
| * by {@link String#valueOf(Object)}. |
| * |
| * @return a string representation of this collection |
| */ |
| public String toString() { |
| Iterator<E> it = iterator(); |
| if (! it.hasNext()) |
| return "[]"; |
| |
| StringBuilder sb = new StringBuilder(); |
| sb.append('['); |
| for (;;) { |
| E e = it.next(); |
| sb.append(e == this ? "(this Collection)" : e); |
| if (! it.hasNext()) |
| return sb.append(']').toString(); |
| sb.append(',').append(' '); |
| } |
| } |
| |
| } |
