diff -r fd16c54261b3 -r 90ce3da70b43 jdk/src/share/classes/java/util/AbstractCollection.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/util/AbstractCollection.java	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,446 @@
+/*
+ * Copyright 1997-2006 Sun Microsystems, Inc.  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.  Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.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> e = iterator();
+        if (o==null) {
+            while (e.hasNext())
+                if (e.next()==null)
+                    return true;
+        } else {
+            while (e.hasNext())
+                if (o.equals(e.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}
+     */
+    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)
+                    return Arrays.copyOf(r, i);
+                r[i] = null; // null-terminate
+                return r;
+            }
+            r[i] = (T)it.next();
+        }
+        return it.hasNext() ? finishToArray(r, it) : r;
+    }
+
+    /**
+     * 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
+     */
+    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 / 2) + 1) * 3;
+                if (newCap <= cap) { // integer overflow
+                    if (cap == Integer.MAX_VALUE)
+                        throw new OutOfMemoryError
+                            ("Required array size too large");
+                    newCap = Integer.MAX_VALUE;
+                }
+                r = Arrays.copyOf(r, newCap);
+            }
+            r[i++] = (T)it.next();
+        }
+        // trim if overallocated
+        return (i == r.length) ? r : Arrays.copyOf(r, i);
+    }
+
+    // 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> e = iterator();
+        if (o==null) {
+            while (e.hasNext()) {
+                if (e.next()==null) {
+                    e.remove();
+                    return true;
+                }
+            }
+        } else {
+            while (e.hasNext()) {
+                if (o.equals(e.next())) {
+                    e.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) {
+        Iterator<?> e = c.iterator();
+        while (e.hasNext())
+            if (!contains(e.next()))
+                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;
+        Iterator<? extends E> e = c.iterator();
+        while (e.hasNext()) {
+            if (add(e.next()))
+                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) {
+        boolean modified = false;
+        Iterator<?> e = iterator();
+        while (e.hasNext()) {
+            if (c.contains(e.next())) {
+                e.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) {
+        boolean modified = false;
+        Iterator<E> e = iterator();
+        while (e.hasNext()) {
+            if (!c.contains(e.next())) {
+                e.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> e = iterator();
+        while (e.hasNext()) {
+            e.next();
+            e.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> i = iterator();
+        if (! i.hasNext())
+            return "[]";
+
+        StringBuilder sb = new StringBuilder();
+        sb.append('[');
+        for (;;) {
+            E e = i.next();
+            sb.append(e == this ? "(this Collection)" : e);
+            if (! i.hasNext())
+                return sb.append(']').toString();
+            sb.append(", ");
+        }
+    }
+
+}