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Comparing jsr166/src/main/java/util/ArrayList.java (file contents):
Revision 1.27 by jsr166, Sun May 18 23:59:57 2008 UTC vs.
Revision 1.44 by jsr166, Wed Nov 16 00:17:25 2016 UTC

# Line 1 | Line 1
1   /*
2 < * Copyright 1997-2007 Sun Microsystems, Inc.  All Rights Reserved.
2 > * Copyright (c) 1997, 2016, 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.  Sun designates this
7 > * published by the Free Software Foundation.  Oracle designates this
8   * particular file as subject to the "Classpath" exception as provided
9 < * by Sun in the LICENSE file that accompanied this code.
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
# Line 18 | Line 18
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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 < * CA 95054 USA or visit www.sun.com if you need additional information or
23 < * have any questions.
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 java.util;
27  
28 + import java.util.function.Consumer;
29 + import java.util.function.Predicate;
30 + import java.util.function.UnaryOperator;
31 +
32   /**
33 < * Resizable-array implementation of the <tt>List</tt> interface.  Implements
33 > * Resizable-array implementation of the {@code List} interface.  Implements
34   * all optional list operations, and permits all elements, including
35 < * <tt>null</tt>.  In addition to implementing the <tt>List</tt> interface,
35 > * {@code null}.  In addition to implementing the {@code List} interface,
36   * this class provides methods to manipulate the size of the array that is
37   * used internally to store the list.  (This class is roughly equivalent to
38 < * <tt>Vector</tt>, except that it is unsynchronized.)
38 > * {@code Vector}, except that it is unsynchronized.)
39   *
40 < * <p>The <tt>size</tt>, <tt>isEmpty</tt>, <tt>get</tt>, <tt>set</tt>,
41 < * <tt>iterator</tt>, and <tt>listIterator</tt> operations run in constant
42 < * time.  The <tt>add</tt> operation runs in <i>amortized constant time</i>,
40 > * <p>The {@code size}, {@code isEmpty}, {@code get}, {@code set},
41 > * {@code iterator}, and {@code listIterator} operations run in constant
42 > * time.  The {@code add} operation runs in <i>amortized constant time</i>,
43   * that is, adding n elements requires O(n) time.  All of the other operations
44   * run in linear time (roughly speaking).  The constant factor is low compared
45 < * to that for the <tt>LinkedList</tt> implementation.
45 > * to that for the {@code LinkedList} implementation.
46   *
47 < * <p>Each <tt>ArrayList</tt> instance has a <i>capacity</i>.  The capacity is
47 > * <p>Each {@code ArrayList} instance has a <i>capacity</i>.  The capacity is
48   * the size of the array used to store the elements in the list.  It is always
49   * at least as large as the list size.  As elements are added to an ArrayList,
50   * its capacity grows automatically.  The details of the growth policy are not
51   * specified beyond the fact that adding an element has constant amortized
52   * time cost.
53   *
54 < * <p>An application can increase the capacity of an <tt>ArrayList</tt> instance
55 < * before adding a large number of elements using the <tt>ensureCapacity</tt>
54 > * <p>An application can increase the capacity of an {@code ArrayList} instance
55 > * before adding a large number of elements using the {@code ensureCapacity}
56   * operation.  This may reduce the amount of incremental reallocation.
57   *
58   * <p><strong>Note that this implementation is not synchronized.</strong>
59 < * If multiple threads access an <tt>ArrayList</tt> instance concurrently,
59 > * If multiple threads access an {@code ArrayList} instance concurrently,
60   * and at least one of the threads modifies the list structurally, it
61   * <i>must</i> be synchronized externally.  (A structural modification is
62   * any operation that adds or deletes one or more elements, or explicitly
# Line 66 | Line 70 | package java.util;
70   * unsynchronized access to the list:<pre>
71   *   List list = Collections.synchronizedList(new ArrayList(...));</pre>
72   *
73 < * <p><a name="fail-fast"/>
73 > * <p id="fail-fast">
74   * The iterators returned by this class's {@link #iterator() iterator} and
75   * {@link #listIterator(int) listIterator} methods are <em>fail-fast</em>:
76   * if the list is structurally modified at any time after the iterator is
# Line 90 | Line 94 | package java.util;
94   * <a href="{@docRoot}/../technotes/guides/collections/index.html">
95   * Java Collections Framework</a>.
96   *
97 + * @param <E> the type of elements in this list
98 + *
99   * @author  Josh Bloch
100   * @author  Neal Gafter
101   * @see     Collection
# Line 98 | Line 104 | package java.util;
104   * @see     Vector
105   * @since   1.2
106   */
101
107   public class ArrayList<E> extends AbstractList<E>
108          implements List<E>, RandomAccess, Cloneable, java.io.Serializable
109   {
110      private static final long serialVersionUID = 8683452581122892189L;
111  
112      /**
113 +     * Default initial capacity.
114 +     */
115 +    private static final int DEFAULT_CAPACITY = 10;
116 +
117 +    /**
118 +     * Shared empty array instance used for empty instances.
119 +     */
120 +    private static final Object[] EMPTY_ELEMENTDATA = {};
121 +
122 +    /**
123 +     * Shared empty array instance used for default sized empty instances. We
124 +     * distinguish this from EMPTY_ELEMENTDATA to know how much to inflate when
125 +     * first element is added.
126 +     */
127 +    private static final Object[] DEFAULTCAPACITY_EMPTY_ELEMENTDATA = {};
128 +
129 +    /**
130       * The array buffer into which the elements of the ArrayList are stored.
131 <     * The capacity of the ArrayList is the length of this array buffer.
131 >     * The capacity of the ArrayList is the length of this array buffer. Any
132 >     * empty ArrayList with elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA
133 >     * will be expanded to DEFAULT_CAPACITY when the first element is added.
134       */
135 <    private transient Object[] elementData;
135 >    transient Object[] elementData; // non-private to simplify nested class access
136  
137      /**
138       * The size of the ArrayList (the number of elements it contains).
# Line 120 | Line 144 | public class ArrayList<E> extends Abstra
144      /**
145       * Constructs an empty list with the specified initial capacity.
146       *
147 <     * @param   initialCapacity   the initial capacity of the list
148 <     * @exception IllegalArgumentException if the specified initial capacity
149 <     *            is negative
147 >     * @param  initialCapacity  the initial capacity of the list
148 >     * @throws IllegalArgumentException if the specified initial capacity
149 >     *         is negative
150       */
151      public ArrayList(int initialCapacity) {
152 <        super();
153 <        if (initialCapacity < 0)
152 >        if (initialCapacity > 0) {
153 >            this.elementData = new Object[initialCapacity];
154 >        } else if (initialCapacity == 0) {
155 >            this.elementData = EMPTY_ELEMENTDATA;
156 >        } else {
157              throw new IllegalArgumentException("Illegal Capacity: "+
158                                                 initialCapacity);
159 <        this.elementData = new Object[initialCapacity];
159 >        }
160      }
161  
162      /**
163       * Constructs an empty list with an initial capacity of ten.
164       */
165      public ArrayList() {
166 <        this(10);
166 >        this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA;
167      }
168  
169      /**
# Line 149 | Line 176 | public class ArrayList<E> extends Abstra
176       */
177      public ArrayList(Collection<? extends E> c) {
178          elementData = c.toArray();
179 <        size = elementData.length;
180 <        // c.toArray might (incorrectly) not return Object[] (see 6260652)
181 <        if (elementData.getClass() != Object[].class)
182 <            elementData = Arrays.copyOf(elementData, size, Object[].class);
179 >        if ((size = elementData.length) != 0) {
180 >            // defend against c.toArray (incorrectly) not returning Object[]
181 >            // (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652)
182 >            if (elementData.getClass() != Object[].class)
183 >                elementData = Arrays.copyOf(elementData, size, Object[].class);
184 >        } else {
185 >            // replace with empty array.
186 >            this.elementData = EMPTY_ELEMENTDATA;
187 >        }
188      }
189  
190      /**
191 <     * Trims the capacity of this <tt>ArrayList</tt> instance to be the
191 >     * Trims the capacity of this {@code ArrayList} instance to be the
192       * list's current size.  An application can use this operation to minimize
193 <     * the storage of an <tt>ArrayList</tt> instance.
193 >     * the storage of an {@code ArrayList} instance.
194       */
195      public void trimToSize() {
196          modCount++;
197 <        int oldCapacity = elementData.length;
198 <        if (size < oldCapacity) {
199 <            elementData = Arrays.copyOf(elementData, size);
197 >        if (size < elementData.length) {
198 >            elementData = (size == 0)
199 >              ? EMPTY_ELEMENTDATA
200 >              : Arrays.copyOf(elementData, size);
201          }
202      }
203  
204      /**
205 <     * Increases the capacity of this <tt>ArrayList</tt> instance, if
205 >     * Increases the capacity of this {@code ArrayList} instance, if
206       * necessary, to ensure that it can hold at least the number of elements
207       * specified by the minimum capacity argument.
208       *
209 <     * @param   minCapacity   the desired minimum capacity
209 >     * @param minCapacity the desired minimum capacity
210       */
211      public void ensureCapacity(int minCapacity) {
212 <        modCount++;
213 <        int oldCapacity = elementData.length;
214 <        if (minCapacity > oldCapacity) {
215 <            Object oldData[] = elementData;
216 <            int newCapacity = (oldCapacity * 3)/2 + 1;
184 <            if (newCapacity < minCapacity)
185 <                newCapacity = minCapacity;
186 <            // minCapacity is usually close to size, so this is a win:
187 <            elementData = Arrays.copyOf(elementData, newCapacity);
212 >        if (minCapacity > elementData.length
213 >            && !(elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA
214 >                 && minCapacity <= DEFAULT_CAPACITY)) {
215 >            modCount++;
216 >            grow(minCapacity);
217          }
218      }
219  
220      /**
221 +     * The maximum size of array to allocate (unless necessary).
222 +     * Some VMs reserve some header words in an array.
223 +     * Attempts to allocate larger arrays may result in
224 +     * OutOfMemoryError: Requested array size exceeds VM limit
225 +     */
226 +    private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
227 +
228 +    /**
229 +     * Increases the capacity to ensure that it can hold at least the
230 +     * number of elements specified by the minimum capacity argument.
231 +     *
232 +     * @param minCapacity the desired minimum capacity
233 +     * @throws OutOfMemoryError if minCapacity is less than zero
234 +     */
235 +    private Object[] grow(int minCapacity) {
236 +        return elementData = Arrays.copyOf(elementData,
237 +                                           newCapacity(minCapacity));
238 +    }
239 +
240 +    private Object[] grow() {
241 +        return grow(size + 1);
242 +    }
243 +
244 +    /**
245 +     * Returns a capacity at least as large as the given minimum capacity.
246 +     * Returns the current capacity increased by 50% if that suffices.
247 +     * Will not return a capacity greater than MAX_ARRAY_SIZE unless
248 +     * the given minimum capacity is greater than MAX_ARRAY_SIZE.
249 +     *
250 +     * @param minCapacity the desired minimum capacity
251 +     * @throws OutOfMemoryError if minCapacity is less than zero
252 +     */
253 +    private int newCapacity(int minCapacity) {
254 +        // overflow-conscious code
255 +        int oldCapacity = elementData.length;
256 +        int newCapacity = oldCapacity + (oldCapacity >> 1);
257 +        if (newCapacity - minCapacity <= 0) {
258 +            if (elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA)
259 +                return Math.max(DEFAULT_CAPACITY, minCapacity);
260 +            if (minCapacity < 0) // overflow
261 +                throw new OutOfMemoryError();
262 +            return minCapacity;
263 +        }
264 +        return (newCapacity - MAX_ARRAY_SIZE <= 0)
265 +            ? newCapacity
266 +            : hugeCapacity(minCapacity);
267 +    }
268 +
269 +    private static int hugeCapacity(int minCapacity) {
270 +        if (minCapacity < 0) // overflow
271 +            throw new OutOfMemoryError();
272 +        return (minCapacity > MAX_ARRAY_SIZE)
273 +            ? Integer.MAX_VALUE
274 +            : MAX_ARRAY_SIZE;
275 +    }
276 +
277 +    /**
278       * Returns the number of elements in this list.
279       *
280       * @return the number of elements in this list
# Line 198 | Line 284 | public class ArrayList<E> extends Abstra
284      }
285  
286      /**
287 <     * Returns <tt>true</tt> if this list contains no elements.
287 >     * Returns {@code true} if this list contains no elements.
288       *
289 <     * @return <tt>true</tt> if this list contains no elements
289 >     * @return {@code true} if this list contains no elements
290       */
291      public boolean isEmpty() {
292          return size == 0;
293      }
294  
295      /**
296 <     * Returns <tt>true</tt> if this list contains the specified element.
297 <     * More formally, returns <tt>true</tt> if and only if this list contains
298 <     * at least one element <tt>e</tt> such that
299 <     * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>.
296 >     * Returns {@code true} if this list contains the specified element.
297 >     * More formally, returns {@code true} if and only if this list contains
298 >     * at least one element {@code e} such that
299 >     * {@code Objects.equals(o, e)}.
300       *
301       * @param o element whose presence in this list is to be tested
302 <     * @return <tt>true</tt> if this list contains the specified element
302 >     * @return {@code true} if this list contains the specified element
303       */
304      public boolean contains(Object o) {
305          return indexOf(o) >= 0;
# Line 222 | Line 308 | public class ArrayList<E> extends Abstra
308      /**
309       * Returns the index of the first occurrence of the specified element
310       * in this list, or -1 if this list does not contain the element.
311 <     * More formally, returns the lowest index <tt>i</tt> such that
312 <     * <tt>(o==null&nbsp;?&nbsp;get(i)==null&nbsp;:&nbsp;o.equals(get(i)))</tt>,
311 >     * More formally, returns the lowest index {@code i} such that
312 >     * {@code Objects.equals(o, get(i))},
313       * or -1 if there is no such index.
314       */
315      public int indexOf(Object o) {
# Line 242 | Line 328 | public class ArrayList<E> extends Abstra
328      /**
329       * Returns the index of the last occurrence of the specified element
330       * in this list, or -1 if this list does not contain the element.
331 <     * More formally, returns the highest index <tt>i</tt> such that
332 <     * <tt>(o==null&nbsp;?&nbsp;get(i)==null&nbsp;:&nbsp;o.equals(get(i)))</tt>,
331 >     * More formally, returns the highest index {@code i} such that
332 >     * {@code Objects.equals(o, get(i))},
333       * or -1 if there is no such index.
334       */
335      public int lastIndexOf(Object o) {
# Line 260 | Line 346 | public class ArrayList<E> extends Abstra
346      }
347  
348      /**
349 <     * Returns a shallow copy of this <tt>ArrayList</tt> instance.  (The
349 >     * Returns a shallow copy of this {@code ArrayList} instance.  (The
350       * elements themselves are not copied.)
351       *
352 <     * @return a clone of this <tt>ArrayList</tt> instance
352 >     * @return a clone of this {@code ArrayList} instance
353       */
354      public Object clone() {
355          try {
356 <            @SuppressWarnings("unchecked")
271 <                ArrayList<E> v = (ArrayList<E>) super.clone();
356 >            ArrayList<?> v = (ArrayList<?>) super.clone();
357              v.elementData = Arrays.copyOf(elementData, size);
358              v.modCount = 0;
359              return v;
360          } catch (CloneNotSupportedException e) {
361              // this shouldn't happen, since we are Cloneable
362 <            throw new InternalError();
362 >            throw new InternalError(e);
363          }
364      }
365  
# Line 307 | Line 392 | public class ArrayList<E> extends Abstra
392       * <p>If the list fits in the specified array with room to spare
393       * (i.e., the array has more elements than the list), the element in
394       * the array immediately following the end of the collection is set to
395 <     * <tt>null</tt>.  (This is useful in determining the length of the
395 >     * {@code null}.  (This is useful in determining the length of the
396       * list <i>only</i> if the caller knows that the list does not contain
397       * any null elements.)
398       *
# Line 338 | Line 423 | public class ArrayList<E> extends Abstra
423          return (E) elementData[index];
424      }
425  
426 +    @SuppressWarnings("unchecked")
427 +    static <E> E elementAt(Object[] es, int index) {
428 +        return (E) es[index];
429 +    }
430 +
431      /**
432       * Returns the element at the specified position in this list.
433       *
# Line 346 | Line 436 | public class ArrayList<E> extends Abstra
436       * @throws IndexOutOfBoundsException {@inheritDoc}
437       */
438      public E get(int index) {
439 <        rangeCheck(index);
350 <
439 >        Objects.checkIndex(index, size);
440          return elementData(index);
441      }
442  
# Line 361 | Line 450 | public class ArrayList<E> extends Abstra
450       * @throws IndexOutOfBoundsException {@inheritDoc}
451       */
452      public E set(int index, E element) {
453 <        rangeCheck(index);
365 <
453 >        Objects.checkIndex(index, size);
454          E oldValue = elementData(index);
455          elementData[index] = element;
456          return oldValue;
457      }
458  
459      /**
460 +     * This helper method split out from add(E) to keep method
461 +     * bytecode size under 35 (the -XX:MaxInlineSize default value),
462 +     * which helps when add(E) is called in a C1-compiled loop.
463 +     */
464 +    private void add(E e, Object[] elementData, int s) {
465 +        if (s == elementData.length)
466 +            elementData = grow();
467 +        elementData[s] = e;
468 +        size = s + 1;
469 +    }
470 +
471 +    /**
472       * Appends the specified element to the end of this list.
473       *
474       * @param e element to be appended to this list
475 <     * @return <tt>true</tt> (as specified by {@link Collection#add})
475 >     * @return {@code true} (as specified by {@link Collection#add})
476       */
477      public boolean add(E e) {
478 <        ensureCapacity(size + 1);  // Increments modCount!!
479 <        elementData[size++] = e;
478 >        modCount++;
479 >        add(e, elementData, size);
480          return true;
481      }
482  
# Line 391 | Line 491 | public class ArrayList<E> extends Abstra
491       */
492      public void add(int index, E element) {
493          rangeCheckForAdd(index);
494 <
495 <        ensureCapacity(size+1);  // Increments modCount!!
496 <        System.arraycopy(elementData, index, elementData, index + 1,
497 <                         size - index);
494 >        modCount++;
495 >        final int s;
496 >        Object[] elementData;
497 >        if ((s = size) == (elementData = this.elementData).length)
498 >            elementData = grow();
499 >        System.arraycopy(elementData, index,
500 >                         elementData, index + 1,
501 >                         s - index);
502          elementData[index] = element;
503 <        size++;
503 >        size = s + 1;
504 >        // checkInvariants();
505      }
506  
507      /**
# Line 409 | Line 514 | public class ArrayList<E> extends Abstra
514       * @throws IndexOutOfBoundsException {@inheritDoc}
515       */
516      public E remove(int index) {
517 <        rangeCheck(index);
517 >        Objects.checkIndex(index, size);
518  
519          modCount++;
520          E oldValue = elementData(index);
# Line 418 | Line 523 | public class ArrayList<E> extends Abstra
523          if (numMoved > 0)
524              System.arraycopy(elementData, index+1, elementData, index,
525                               numMoved);
526 <        elementData[--size] = null; // Let gc do its work
526 >        elementData[--size] = null; // clear to let GC do its work
527  
528 +        // checkInvariants();
529          return oldValue;
530      }
531  
# Line 427 | Line 533 | public class ArrayList<E> extends Abstra
533       * Removes the first occurrence of the specified element from this list,
534       * if it is present.  If the list does not contain the element, it is
535       * unchanged.  More formally, removes the element with the lowest index
536 <     * <tt>i</tt> such that
537 <     * <tt>(o==null&nbsp;?&nbsp;get(i)==null&nbsp;:&nbsp;o.equals(get(i)))</tt>
538 <     * (if such an element exists).  Returns <tt>true</tt> if this list
536 >     * {@code i} such that
537 >     * {@code Objects.equals(o, get(i))}
538 >     * (if such an element exists).  Returns {@code true} if this list
539       * contained the specified element (or equivalently, if this list
540       * changed as a result of the call).
541       *
542       * @param o element to be removed from this list, if present
543 <     * @return <tt>true</tt> if this list contained the specified element
543 >     * @return {@code true} if this list contained the specified element
544       */
545      public boolean remove(Object o) {
546          if (o == null) {
# Line 453 | Line 559 | public class ArrayList<E> extends Abstra
559          return false;
560      }
561  
562 <    /*
562 >    /**
563       * Private remove method that skips bounds checking and does not
564       * return the value removed.
565       */
# Line 463 | Line 569 | public class ArrayList<E> extends Abstra
569          if (numMoved > 0)
570              System.arraycopy(elementData, index+1, elementData, index,
571                               numMoved);
572 <        elementData[--size] = null; // Let gc do its work
572 >        elementData[--size] = null; // clear to let GC do its work
573      }
574  
575      /**
# Line 472 | Line 578 | public class ArrayList<E> extends Abstra
578       */
579      public void clear() {
580          modCount++;
581 <
476 <        // Let gc do its work
477 <        for (int i = 0; i < size; i++)
478 <            elementData[i] = null;
479 <
581 >        Arrays.fill(elementData, 0, size, null);
582          size = 0;
583      }
584  
# Line 490 | Line 592 | public class ArrayList<E> extends Abstra
592       * list is nonempty.)
593       *
594       * @param c collection containing elements to be added to this list
595 <     * @return <tt>true</tt> if this list changed as a result of the call
595 >     * @return {@code true} if this list changed as a result of the call
596       * @throws NullPointerException if the specified collection is null
597       */
598      public boolean addAll(Collection<? extends E> c) {
599          Object[] a = c.toArray();
600 +        modCount++;
601          int numNew = a.length;
602 <        ensureCapacity(size + numNew);  // Increments modCount
603 <        System.arraycopy(a, 0, elementData, size, numNew);
604 <        size += numNew;
605 <        return numNew != 0;
602 >        if (numNew == 0)
603 >            return false;
604 >        Object[] elementData;
605 >        final int s;
606 >        if (numNew > (elementData = this.elementData).length - (s = size))
607 >            elementData = grow(s + numNew);
608 >        System.arraycopy(a, 0, elementData, s, numNew);
609 >        size = s + numNew;
610 >        // checkInvariants();
611 >        return true;
612      }
613  
614      /**
# Line 513 | Line 622 | public class ArrayList<E> extends Abstra
622       * @param index index at which to insert the first element from the
623       *              specified collection
624       * @param c collection containing elements to be added to this list
625 <     * @return <tt>true</tt> if this list changed as a result of the call
625 >     * @return {@code true} if this list changed as a result of the call
626       * @throws IndexOutOfBoundsException {@inheritDoc}
627       * @throws NullPointerException if the specified collection is null
628       */
# Line 521 | Line 630 | public class ArrayList<E> extends Abstra
630          rangeCheckForAdd(index);
631  
632          Object[] a = c.toArray();
633 +        modCount++;
634          int numNew = a.length;
635 <        ensureCapacity(size + numNew);  // Increments modCount
635 >        if (numNew == 0)
636 >            return false;
637 >        Object[] elementData;
638 >        final int s;
639 >        if (numNew > (elementData = this.elementData).length - (s = size))
640 >            elementData = grow(s + numNew);
641  
642 <        int numMoved = size - index;
642 >        int numMoved = s - index;
643          if (numMoved > 0)
644 <            System.arraycopy(elementData, index, elementData, index + numNew,
644 >            System.arraycopy(elementData, index,
645 >                             elementData, index + numNew,
646                               numMoved);
531
647          System.arraycopy(a, 0, elementData, index, numNew);
648 <        size += numNew;
649 <        return numNew != 0;
648 >        size = s + numNew;
649 >        // checkInvariants();
650 >        return true;
651      }
652  
653      /**
# Line 544 | Line 660 | public class ArrayList<E> extends Abstra
660       * @throws IndexOutOfBoundsException if {@code fromIndex} or
661       *         {@code toIndex} is out of range
662       *         ({@code fromIndex < 0 ||
547     *          fromIndex >= size() ||
663       *          toIndex > size() ||
664       *          toIndex < fromIndex})
665       */
666      protected void removeRange(int fromIndex, int toIndex) {
667 +        if (fromIndex > toIndex) {
668 +            throw new IndexOutOfBoundsException(
669 +                    outOfBoundsMsg(fromIndex, toIndex));
670 +        }
671          modCount++;
672 <        int numMoved = size - toIndex;
673 <        System.arraycopy(elementData, toIndex, elementData, fromIndex,
674 <                         numMoved);
675 <
676 <        // Let gc do its work
558 <        int newSize = size - (toIndex-fromIndex);
559 <        while (size != newSize)
560 <            elementData[--size] = null;
561 <    }
562 <
563 <    /**
564 <     * Checks if the given index is in range.  If not, throws an appropriate
565 <     * runtime exception.  This method does *not* check if the index is
566 <     * negative: It is always used immediately prior to an array access,
567 <     * which throws an ArrayIndexOutOfBoundsException if index is negative.
568 <     */
569 <    private void rangeCheck(int index) {
570 <        if (index >= size)
571 <            throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
672 >        final Object[] es = elementData;
673 >        final int oldSize = size;
674 >        System.arraycopy(es, toIndex, es, fromIndex, oldSize - toIndex);
675 >        Arrays.fill(es, size -= (toIndex - fromIndex), oldSize, null);
676 >        // checkInvariants();
677      }
678  
679      /**
# Line 589 | Line 694 | public class ArrayList<E> extends Abstra
694      }
695  
696      /**
697 +     * A version used in checking (fromIndex > toIndex) condition
698 +     */
699 +    private static String outOfBoundsMsg(int fromIndex, int toIndex) {
700 +        return "From Index: " + fromIndex + " > To Index: " + toIndex;
701 +    }
702 +
703 +    /**
704       * Removes from this list all of its elements that are contained in the
705       * specified collection.
706       *
707       * @param c collection containing elements to be removed from this list
708       * @return {@code true} if this list changed as a result of the call
709       * @throws ClassCastException if the class of an element of this list
710 <     *         is incompatible with the specified collection (optional)
710 >     *         is incompatible with the specified collection
711 >     * (<a href="Collection.html#optional-restrictions">optional</a>)
712       * @throws NullPointerException if this list contains a null element and the
713 <     *         specified collection does not permit null elements (optional),
713 >     *         specified collection does not permit null elements
714 >     * (<a href="Collection.html#optional-restrictions">optional</a>),
715       *         or if the specified collection is null
716       * @see Collection#contains(Object)
717       */
718      public boolean removeAll(Collection<?> c) {
719 <        return batchRemove(c, false);
719 >        return batchRemove(c, false, 0, size);
720      }
721  
722      /**
# Line 613 | Line 727 | public class ArrayList<E> extends Abstra
727       * @param c collection containing elements to be retained in this list
728       * @return {@code true} if this list changed as a result of the call
729       * @throws ClassCastException if the class of an element of this list
730 <     *         is incompatible with the specified collection (optional)
730 >     *         is incompatible with the specified collection
731 >     * (<a href="Collection.html#optional-restrictions">optional</a>)
732       * @throws NullPointerException if this list contains a null element and the
733 <     *         specified collection does not permit null elements (optional),
733 >     *         specified collection does not permit null elements
734 >     * (<a href="Collection.html#optional-restrictions">optional</a>),
735       *         or if the specified collection is null
736       * @see Collection#contains(Object)
737       */
738      public boolean retainAll(Collection<?> c) {
739 <        return batchRemove(c, true);
739 >        return batchRemove(c, true, 0, size);
740      }
741  
742 <    private boolean batchRemove(Collection<?> c, boolean complement) {
743 <        final Object[] elementData = this.elementData;
744 <        int r = 0, w = 0;
745 <        boolean modified = false;
746 <        try {
747 <            for (; r < size; r++)
748 <                if (c.contains(elementData[r]) == complement)
749 <                    elementData[w++] = elementData[r];
750 <        } finally {
751 <            // Preserve behavioral compatibility with AbstractCollection,
752 <            // even if c.contains() throws.
753 <            if (r != size) {
754 <                System.arraycopy(elementData, r,
755 <                                 elementData, w,
756 <                                 size - r);
757 <                w += size - r;
758 <            }
759 <            if (w != size) {
760 <                for (int i = w; i < size; i++)
761 <                    elementData[i] = null;
762 <                modCount += size - w;
763 <                size = w;
764 <                modified = true;
742 >    boolean batchRemove(Collection<?> c, boolean complement,
743 >                        final int from, final int end) {
744 >        Objects.requireNonNull(c);
745 >        final Object[] es = elementData;
746 >        final boolean modified;
747 >        int r;
748 >        // Optimize for initial run of survivors
749 >        for (r = from; r < end && c.contains(es[r]) == complement; r++)
750 >            ;
751 >        if (modified = (r < end)) {
752 >            int w = r++;
753 >            try {
754 >                for (Object e; r < end; r++)
755 >                    if (c.contains(e = es[r]) == complement)
756 >                        es[w++] = e;
757 >            } catch (Throwable ex) {
758 >                // Preserve behavioral compatibility with AbstractCollection,
759 >                // even if c.contains() throws.
760 >                System.arraycopy(es, r, es, w, end - r);
761 >                w += end - r;
762 >                throw ex;
763 >            } finally {
764 >                final int oldSize = size, deleted = end - w;
765 >                modCount += deleted;
766 >                System.arraycopy(es, end, es, w, oldSize - end);
767 >                Arrays.fill(es, size -= deleted, oldSize, null);
768              }
769          }
770 +        // checkInvariants();
771          return modified;
772      }
773  
774      /**
775 <     * Save the state of the <tt>ArrayList</tt> instance to a stream (that
775 >     * Save the state of the {@code ArrayList} instance to a stream (that
776       * is, serialize it).
777       *
778 <     * @serialData The length of the array backing the <tt>ArrayList</tt>
778 >     * @serialData The length of the array backing the {@code ArrayList}
779       *             instance is emitted (int), followed by all of its elements
780 <     *             (each an <tt>Object</tt>) in the proper order.
780 >     *             (each an {@code Object}) in the proper order.
781       */
782      private void writeObject(java.io.ObjectOutputStream s)
783          throws java.io.IOException{
# Line 665 | Line 785 | public class ArrayList<E> extends Abstra
785          int expectedModCount = modCount;
786          s.defaultWriteObject();
787  
788 <        // Write out array length
789 <        s.writeInt(elementData.length);
788 >        // Write out size as capacity for behavioural compatibility with clone()
789 >        s.writeInt(size);
790  
791          // Write out all elements in the proper order.
792 <        for (int i=0; i<size; i++)
792 >        for (int i=0; i<size; i++) {
793              s.writeObject(elementData[i]);
794 +        }
795  
796          if (modCount != expectedModCount) {
797              throw new ConcurrentModificationException();
798          }
678
799      }
800  
801      /**
802 <     * Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
802 >     * Reconstitute the {@code ArrayList} instance from a stream (that is,
803       * deserialize it).
804       */
805      private void readObject(java.io.ObjectInputStream s)
806          throws java.io.IOException, ClassNotFoundException {
807 +
808          // Read in size, and any hidden stuff
809          s.defaultReadObject();
810  
811 <        // Read in array length and allocate array
812 <        int arrayLength = s.readInt();
813 <        Object[] a = elementData = new Object[arrayLength];
814 <
815 <        // Read in all elements in the proper order.
816 <        for (int i=0; i<size; i++)
817 <            a[i] = s.readObject();
811 >        // Read in capacity
812 >        s.readInt(); // ignored
813 >
814 >        if (size > 0) {
815 >            // like clone(), allocate array based upon size not capacity
816 >            Object[] elements = new Object[size];
817 >
818 >            // Read in all elements in the proper order.
819 >            for (int i = 0; i < size; i++) {
820 >                elements[i] = s.readObject();
821 >            }
822 >
823 >            elementData = elements;
824 >        } else if (size == 0) {
825 >            elementData = EMPTY_ELEMENTDATA;
826 >        } else {
827 >            throw new java.io.InvalidObjectException("Invalid size: " + size);
828 >        }
829      }
830  
831      /**
# Line 709 | Line 841 | public class ArrayList<E> extends Abstra
841       * @throws IndexOutOfBoundsException {@inheritDoc}
842       */
843      public ListIterator<E> listIterator(int index) {
844 <        if (index < 0 || index > size)
713 <            throw new IndexOutOfBoundsException("Index: "+index);
844 >        rangeCheckForAdd(index);
845          return new ListItr(index);
846      }
847  
# Line 745 | Line 876 | public class ArrayList<E> extends Abstra
876          int lastRet = -1; // index of last element returned; -1 if no such
877          int expectedModCount = modCount;
878  
879 +        // prevent creating a synthetic constructor
880 +        Itr() {}
881 +
882          public boolean hasNext() {
883              return cursor != size;
884          }
# Line 777 | Line 911 | public class ArrayList<E> extends Abstra
911              }
912          }
913  
914 +        @Override
915 +        public void forEachRemaining(Consumer<? super E> action) {
916 +            Objects.requireNonNull(action);
917 +            final int size = ArrayList.this.size;
918 +            int i = cursor;
919 +            if (i < size) {
920 +                final Object[] es = elementData;
921 +                if (i >= es.length)
922 +                    throw new ConcurrentModificationException();
923 +                for (; i < size && modCount == expectedModCount; i++)
924 +                    action.accept(elementAt(es, i));
925 +                // update once at end to reduce heap write traffic
926 +                cursor = i;
927 +                lastRet = i - 1;
928 +                checkForComodification();
929 +            }
930 +        }
931 +
932          final void checkForComodification() {
933              if (modCount != expectedModCount)
934                  throw new ConcurrentModificationException();
# Line 875 | Line 1027 | public class ArrayList<E> extends Abstra
1027       */
1028      public List<E> subList(int fromIndex, int toIndex) {
1029          subListRangeCheck(fromIndex, toIndex, size);
1030 <        return new SubList(this, 0, fromIndex, toIndex);
1030 >        return new SubList<>(this, fromIndex, toIndex);
1031      }
1032  
1033 <    static void subListRangeCheck(int fromIndex, int toIndex, int size) {
1034 <        if (fromIndex < 0)
1035 <            throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
884 <        if (toIndex > size)
885 <            throw new IndexOutOfBoundsException("toIndex = " + toIndex);
886 <        if (fromIndex > toIndex)
887 <            throw new IllegalArgumentException("fromIndex(" + fromIndex +
888 <                                               ") > toIndex(" + toIndex + ")");
889 <    }
890 <
891 <    private class SubList extends AbstractList<E> implements RandomAccess {
892 <        private final AbstractList<E> parent;
893 <        private final int parentOffset;
1033 >    private static class SubList<E> extends AbstractList<E> implements RandomAccess {
1034 >        private final ArrayList<E> root;
1035 >        private final SubList<E> parent;
1036          private final int offset;
1037          private int size;
1038  
1039 <        SubList(AbstractList<E> parent,
1040 <                int offset, int fromIndex, int toIndex) {
1039 >        /**
1040 >         * Constructs a sublist of an arbitrary ArrayList.
1041 >         */
1042 >        public SubList(ArrayList<E> root, int fromIndex, int toIndex) {
1043 >            this.root = root;
1044 >            this.parent = null;
1045 >            this.offset = fromIndex;
1046 >            this.size = toIndex - fromIndex;
1047 >            this.modCount = root.modCount;
1048 >        }
1049 >
1050 >        /**
1051 >         * Constructs a sublist of another SubList.
1052 >         */
1053 >        private SubList(SubList<E> parent, int fromIndex, int toIndex) {
1054 >            this.root = parent.root;
1055              this.parent = parent;
1056 <            this.parentOffset = fromIndex;
901 <            this.offset = offset + fromIndex;
1056 >            this.offset = parent.offset + fromIndex;
1057              this.size = toIndex - fromIndex;
1058 <            this.modCount = ArrayList.this.modCount;
1058 >            this.modCount = root.modCount;
1059          }
1060  
1061 <        public E set(int index, E e) {
1062 <            rangeCheck(index);
1061 >        public E set(int index, E element) {
1062 >            Objects.checkIndex(index, size);
1063              checkForComodification();
1064 <            E oldValue = ArrayList.this.elementData(offset + index);
1065 <            ArrayList.this.elementData[offset + index] = e;
1064 >            E oldValue = root.elementData(offset + index);
1065 >            root.elementData[offset + index] = element;
1066              return oldValue;
1067          }
1068  
1069          public E get(int index) {
1070 <            rangeCheck(index);
1070 >            Objects.checkIndex(index, size);
1071              checkForComodification();
1072 <            return ArrayList.this.elementData(offset + index);
1072 >            return root.elementData(offset + index);
1073          }
1074  
1075          public int size() {
1076              checkForComodification();
1077 <            return this.size;
1077 >            return size;
1078          }
1079  
1080 <        public void add(int index, E e) {
1080 >        public void add(int index, E element) {
1081              rangeCheckForAdd(index);
1082              checkForComodification();
1083 <            parent.add(parentOffset + index, e);
1084 <            this.modCount = parent.modCount;
930 <            this.size++;
1083 >            root.add(offset + index, element);
1084 >            updateSizeAndModCount(1);
1085          }
1086  
1087          public E remove(int index) {
1088 <            rangeCheck(index);
1088 >            Objects.checkIndex(index, size);
1089              checkForComodification();
1090 <            E result = parent.remove(parentOffset + index);
1091 <            this.modCount = parent.modCount;
938 <            this.size--;
1090 >            E result = root.remove(offset + index);
1091 >            updateSizeAndModCount(-1);
1092              return result;
1093          }
1094  
1095          protected void removeRange(int fromIndex, int toIndex) {
1096              checkForComodification();
1097 <            parent.removeRange(parentOffset + fromIndex,
1098 <                               parentOffset + toIndex);
946 <            this.modCount = parent.modCount;
947 <            this.size -= toIndex - fromIndex;
1097 >            root.removeRange(offset + fromIndex, offset + toIndex);
1098 >            updateSizeAndModCount(fromIndex - toIndex);
1099          }
1100  
1101          public boolean addAll(Collection<? extends E> c) {
# Line 956 | Line 1107 | public class ArrayList<E> extends Abstra
1107              int cSize = c.size();
1108              if (cSize==0)
1109                  return false;
959
1110              checkForComodification();
1111 <            parent.addAll(parentOffset + index, c);
1112 <            this.modCount = parent.modCount;
963 <            this.size += cSize;
1111 >            root.addAll(offset + index, c);
1112 >            updateSizeAndModCount(cSize);
1113              return true;
1114          }
1115  
1116 +        public boolean removeAll(Collection<?> c) {
1117 +            return batchRemove(c, false);
1118 +        }
1119 +
1120 +        public boolean retainAll(Collection<?> c) {
1121 +            return batchRemove(c, true);
1122 +        }
1123 +
1124 +        private boolean batchRemove(Collection<?> c, boolean complement) {
1125 +            checkForComodification();
1126 +            int oldSize = root.size;
1127 +            boolean modified =
1128 +                root.batchRemove(c, complement, offset, offset + size);
1129 +            if (modified)
1130 +                updateSizeAndModCount(root.size - oldSize);
1131 +            return modified;
1132 +        }
1133 +
1134 +        public boolean removeIf(Predicate<? super E> filter) {
1135 +            checkForComodification();
1136 +            int oldSize = root.size;
1137 +            boolean modified = root.removeIf(filter, offset, offset + size);
1138 +            if (modified)
1139 +                updateSizeAndModCount(root.size - oldSize);
1140 +            return modified;
1141 +        }
1142 +
1143          public Iterator<E> iterator() {
1144              return listIterator();
1145          }
1146  
1147 <        public ListIterator<E> listIterator(final int index) {
1147 >        public ListIterator<E> listIterator(int index) {
1148              checkForComodification();
1149              rangeCheckForAdd(index);
1150  
1151              return new ListIterator<E>() {
1152                  int cursor = index;
1153                  int lastRet = -1;
1154 <                int expectedModCount = ArrayList.this.modCount;
1154 >                int expectedModCount = root.modCount;
1155  
1156                  public boolean hasNext() {
1157                      return cursor != SubList.this.size;
# Line 987 | Line 1163 | public class ArrayList<E> extends Abstra
1163                      int i = cursor;
1164                      if (i >= SubList.this.size)
1165                          throw new NoSuchElementException();
1166 <                    Object[] elementData = ArrayList.this.elementData;
1166 >                    Object[] elementData = root.elementData;
1167                      if (offset + i >= elementData.length)
1168                          throw new ConcurrentModificationException();
1169                      cursor = i + 1;
# Line 1004 | Line 1180 | public class ArrayList<E> extends Abstra
1180                      int i = cursor - 1;
1181                      if (i < 0)
1182                          throw new NoSuchElementException();
1183 <                    Object[] elementData = ArrayList.this.elementData;
1183 >                    Object[] elementData = root.elementData;
1184                      if (offset + i >= elementData.length)
1185                          throw new ConcurrentModificationException();
1186                      cursor = i;
1187                      return (E) elementData[offset + (lastRet = i)];
1188                  }
1189  
1190 +                public void forEachRemaining(Consumer<? super E> action) {
1191 +                    Objects.requireNonNull(action);
1192 +                    final int size = SubList.this.size;
1193 +                    int i = cursor;
1194 +                    if (i < size) {
1195 +                        final Object[] es = root.elementData;
1196 +                        if (offset + i >= es.length)
1197 +                            throw new ConcurrentModificationException();
1198 +                        for (; i < size && modCount == expectedModCount; i++)
1199 +                            action.accept(elementAt(es, offset + i));
1200 +                        // update once at end to reduce heap write traffic
1201 +                        cursor = i;
1202 +                        lastRet = i - 1;
1203 +                        checkForComodification();
1204 +                    }
1205 +                }
1206 +
1207                  public int nextIndex() {
1208                      return cursor;
1209                  }
# Line 1028 | Line 1221 | public class ArrayList<E> extends Abstra
1221                          SubList.this.remove(lastRet);
1222                          cursor = lastRet;
1223                          lastRet = -1;
1224 <                        expectedModCount = ArrayList.this.modCount;
1224 >                        expectedModCount = root.modCount;
1225                      } catch (IndexOutOfBoundsException ex) {
1226                          throw new ConcurrentModificationException();
1227                      }
# Line 1040 | Line 1233 | public class ArrayList<E> extends Abstra
1233                      checkForComodification();
1234  
1235                      try {
1236 <                        ArrayList.this.set(offset + lastRet, e);
1236 >                        root.set(offset + lastRet, e);
1237                      } catch (IndexOutOfBoundsException ex) {
1238                          throw new ConcurrentModificationException();
1239                      }
# Line 1054 | Line 1247 | public class ArrayList<E> extends Abstra
1247                          SubList.this.add(i, e);
1248                          cursor = i + 1;
1249                          lastRet = -1;
1250 <                        expectedModCount = ArrayList.this.modCount;
1250 >                        expectedModCount = root.modCount;
1251                      } catch (IndexOutOfBoundsException ex) {
1252                          throw new ConcurrentModificationException();
1253                      }
1254                  }
1255  
1256                  final void checkForComodification() {
1257 <                    if (expectedModCount != ArrayList.this.modCount)
1257 >                    if (root.modCount != expectedModCount)
1258                          throw new ConcurrentModificationException();
1259                  }
1260              };
# Line 1069 | Line 1262 | public class ArrayList<E> extends Abstra
1262  
1263          public List<E> subList(int fromIndex, int toIndex) {
1264              subListRangeCheck(fromIndex, toIndex, size);
1265 <            return new SubList(this, offset, fromIndex, toIndex);
1073 <        }
1074 <
1075 <        private void rangeCheck(int index) {
1076 <            if (index < 0 || index >= this.size)
1077 <                throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
1265 >            return new SubList<>(this, fromIndex, toIndex);
1266          }
1267  
1268          private void rangeCheckForAdd(int index) {
# Line 1087 | Line 1275 | public class ArrayList<E> extends Abstra
1275          }
1276  
1277          private void checkForComodification() {
1278 <            if (ArrayList.this.modCount != this.modCount)
1278 >            if (root.modCount != modCount)
1279                  throw new ConcurrentModificationException();
1280          }
1281 +
1282 +        private void updateSizeAndModCount(int sizeChange) {
1283 +            SubList<E> slist = this;
1284 +            do {
1285 +                slist.size += sizeChange;
1286 +                slist.modCount = root.modCount;
1287 +                slist = slist.parent;
1288 +            } while (slist != null);
1289 +        }
1290 +
1291 +        public Spliterator<E> spliterator() {
1292 +            checkForComodification();
1293 +
1294 +            // ArrayListSpliterator is not used because late-binding logic
1295 +            // is different here
1296 +            return new Spliterator<>() {
1297 +                private int index = offset; // current index, modified on advance/split
1298 +                private int fence = -1; // -1 until used; then one past last index
1299 +                private int expectedModCount; // initialized when fence set
1300 +
1301 +                private int getFence() { // initialize fence to size on first use
1302 +                    int hi; // (a specialized variant appears in method forEach)
1303 +                    if ((hi = fence) < 0) {
1304 +                        expectedModCount = modCount;
1305 +                        hi = fence = offset + size;
1306 +                    }
1307 +                    return hi;
1308 +                }
1309 +
1310 +                public ArrayListSpliterator<E> trySplit() {
1311 +                    int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1312 +                    // ArrayListSpliterator could be used here as the source is already bound
1313 +                    return (lo >= mid) ? null : // divide range in half unless too small
1314 +                        new ArrayListSpliterator<>(root, lo, index = mid,
1315 +                                                   expectedModCount);
1316 +                }
1317 +
1318 +                public boolean tryAdvance(Consumer<? super E> action) {
1319 +                    Objects.requireNonNull(action);
1320 +                    int hi = getFence(), i = index;
1321 +                    if (i < hi) {
1322 +                        index = i + 1;
1323 +                        @SuppressWarnings("unchecked") E e = (E)root.elementData[i];
1324 +                        action.accept(e);
1325 +                        if (root.modCount != expectedModCount)
1326 +                            throw new ConcurrentModificationException();
1327 +                        return true;
1328 +                    }
1329 +                    return false;
1330 +                }
1331 +
1332 +                public void forEachRemaining(Consumer<? super E> action) {
1333 +                    Objects.requireNonNull(action);
1334 +                    int i, hi, mc; // hoist accesses and checks from loop
1335 +                    ArrayList<E> lst = root;
1336 +                    Object[] a;
1337 +                    if ((a = lst.elementData) != null) {
1338 +                        if ((hi = fence) < 0) {
1339 +                            mc = modCount;
1340 +                            hi = offset + size;
1341 +                        }
1342 +                        else
1343 +                            mc = expectedModCount;
1344 +                        if ((i = index) >= 0 && (index = hi) <= a.length) {
1345 +                            for (; i < hi; ++i) {
1346 +                                @SuppressWarnings("unchecked") E e = (E) a[i];
1347 +                                action.accept(e);
1348 +                            }
1349 +                            if (lst.modCount == mc)
1350 +                                return;
1351 +                        }
1352 +                    }
1353 +                    throw new ConcurrentModificationException();
1354 +                }
1355 +
1356 +                public long estimateSize() {
1357 +                    return (long) (getFence() - index);
1358 +                }
1359 +
1360 +                public int characteristics() {
1361 +                    return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
1362 +                }
1363 +            };
1364 +        }
1365 +    }
1366 +
1367 +    @Override
1368 +    public void forEach(Consumer<? super E> action) {
1369 +        Objects.requireNonNull(action);
1370 +        final int expectedModCount = modCount;
1371 +        final Object[] es = elementData;
1372 +        final int size = this.size;
1373 +        for (int i = 0; modCount == expectedModCount && i < size; i++)
1374 +            action.accept(elementAt(es, i));
1375 +        if (modCount != expectedModCount)
1376 +            throw new ConcurrentModificationException();
1377 +    }
1378 +
1379 +    /**
1380 +     * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
1381 +     * and <em>fail-fast</em> {@link Spliterator} over the elements in this
1382 +     * list.
1383 +     *
1384 +     * <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
1385 +     * {@link Spliterator#SUBSIZED}, and {@link Spliterator#ORDERED}.
1386 +     * Overriding implementations should document the reporting of additional
1387 +     * characteristic values.
1388 +     *
1389 +     * @return a {@code Spliterator} over the elements in this list
1390 +     * @since 1.8
1391 +     */
1392 +    @Override
1393 +    public Spliterator<E> spliterator() {
1394 +        return new ArrayListSpliterator<>(this, 0, -1, 0);
1395 +    }
1396 +
1397 +    /** Index-based split-by-two, lazily initialized Spliterator */
1398 +    static final class ArrayListSpliterator<E> implements Spliterator<E> {
1399 +
1400 +        /*
1401 +         * If ArrayLists were immutable, or structurally immutable (no
1402 +         * adds, removes, etc), we could implement their spliterators
1403 +         * with Arrays.spliterator. Instead we detect as much
1404 +         * interference during traversal as practical without
1405 +         * sacrificing much performance. We rely primarily on
1406 +         * modCounts. These are not guaranteed to detect concurrency
1407 +         * violations, and are sometimes overly conservative about
1408 +         * within-thread interference, but detect enough problems to
1409 +         * be worthwhile in practice. To carry this out, we (1) lazily
1410 +         * initialize fence and expectedModCount until the latest
1411 +         * point that we need to commit to the state we are checking
1412 +         * against; thus improving precision.  (This doesn't apply to
1413 +         * SubLists, that create spliterators with current non-lazy
1414 +         * values).  (2) We perform only a single
1415 +         * ConcurrentModificationException check at the end of forEach
1416 +         * (the most performance-sensitive method). When using forEach
1417 +         * (as opposed to iterators), we can normally only detect
1418 +         * interference after actions, not before. Further
1419 +         * CME-triggering checks apply to all other possible
1420 +         * violations of assumptions for example null or too-small
1421 +         * elementData array given its size(), that could only have
1422 +         * occurred due to interference.  This allows the inner loop
1423 +         * of forEach to run without any further checks, and
1424 +         * simplifies lambda-resolution. While this does entail a
1425 +         * number of checks, note that in the common case of
1426 +         * list.stream().forEach(a), no checks or other computation
1427 +         * occur anywhere other than inside forEach itself.  The other
1428 +         * less-often-used methods cannot take advantage of most of
1429 +         * these streamlinings.
1430 +         */
1431 +
1432 +        private final ArrayList<E> list;
1433 +        private int index; // current index, modified on advance/split
1434 +        private int fence; // -1 until used; then one past last index
1435 +        private int expectedModCount; // initialized when fence set
1436 +
1437 +        /** Create new spliterator covering the given range */
1438 +        ArrayListSpliterator(ArrayList<E> list, int origin, int fence,
1439 +                             int expectedModCount) {
1440 +            this.list = list; // OK if null unless traversed
1441 +            this.index = origin;
1442 +            this.fence = fence;
1443 +            this.expectedModCount = expectedModCount;
1444 +        }
1445 +
1446 +        private int getFence() { // initialize fence to size on first use
1447 +            int hi; // (a specialized variant appears in method forEach)
1448 +            ArrayList<E> lst;
1449 +            if ((hi = fence) < 0) {
1450 +                if ((lst = list) == null)
1451 +                    hi = fence = 0;
1452 +                else {
1453 +                    expectedModCount = lst.modCount;
1454 +                    hi = fence = lst.size;
1455 +                }
1456 +            }
1457 +            return hi;
1458 +        }
1459 +
1460 +        public ArrayListSpliterator<E> trySplit() {
1461 +            int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1462 +            return (lo >= mid) ? null : // divide range in half unless too small
1463 +                new ArrayListSpliterator<>(list, lo, index = mid,
1464 +                                           expectedModCount);
1465 +        }
1466 +
1467 +        public boolean tryAdvance(Consumer<? super E> action) {
1468 +            if (action == null)
1469 +                throw new NullPointerException();
1470 +            int hi = getFence(), i = index;
1471 +            if (i < hi) {
1472 +                index = i + 1;
1473 +                @SuppressWarnings("unchecked") E e = (E)list.elementData[i];
1474 +                action.accept(e);
1475 +                if (list.modCount != expectedModCount)
1476 +                    throw new ConcurrentModificationException();
1477 +                return true;
1478 +            }
1479 +            return false;
1480 +        }
1481 +
1482 +        public void forEachRemaining(Consumer<? super E> action) {
1483 +            int i, hi, mc; // hoist accesses and checks from loop
1484 +            ArrayList<E> lst; Object[] a;
1485 +            if (action == null)
1486 +                throw new NullPointerException();
1487 +            if ((lst = list) != null && (a = lst.elementData) != null) {
1488 +                if ((hi = fence) < 0) {
1489 +                    mc = lst.modCount;
1490 +                    hi = lst.size;
1491 +                }
1492 +                else
1493 +                    mc = expectedModCount;
1494 +                if ((i = index) >= 0 && (index = hi) <= a.length) {
1495 +                    for (; i < hi; ++i) {
1496 +                        @SuppressWarnings("unchecked") E e = (E) a[i];
1497 +                        action.accept(e);
1498 +                    }
1499 +                    if (lst.modCount == mc)
1500 +                        return;
1501 +                }
1502 +            }
1503 +            throw new ConcurrentModificationException();
1504 +        }
1505 +
1506 +        public long estimateSize() {
1507 +            return (long) (getFence() - index);
1508 +        }
1509 +
1510 +        public int characteristics() {
1511 +            return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
1512 +        }
1513 +    }
1514 +
1515 +    // A tiny bit set implementation
1516 +
1517 +    private static long[] nBits(int n) {
1518 +        return new long[((n - 1) >> 6) + 1];
1519 +    }
1520 +    private static void setBit(long[] bits, int i) {
1521 +        bits[i >> 6] |= 1L << i;
1522 +    }
1523 +    private static boolean isClear(long[] bits, int i) {
1524 +        return (bits[i >> 6] & (1L << i)) == 0;
1525 +    }
1526 +
1527 +    @Override
1528 +    public boolean removeIf(Predicate<? super E> filter) {
1529 +        return removeIf(filter, 0, size);
1530 +    }
1531 +
1532 +    /**
1533 +     * Removes all elements satisfying the given predicate, from index
1534 +     * i (inclusive) to index end (exclusive).
1535 +     */
1536 +    boolean removeIf(Predicate<? super E> filter, int i, final int end) {
1537 +        Objects.requireNonNull(filter);
1538 +        int expectedModCount = modCount;
1539 +        final Object[] es = elementData;
1540 +        // Optimize for initial run of survivors
1541 +        for (; i < end && !filter.test(elementAt(es, i)); i++)
1542 +            ;
1543 +        // Tolerate predicates that reentrantly access the collection for
1544 +        // read (but writers still get CME), so traverse once to find
1545 +        // elements to delete, a second pass to physically expunge.
1546 +        if (i < end) {
1547 +            final int beg = i;
1548 +            final long[] deathRow = nBits(end - beg);
1549 +            deathRow[0] = 1L;   // set bit 0
1550 +            for (i = beg + 1; i < end; i++)
1551 +                if (filter.test(elementAt(es, i)))
1552 +                    setBit(deathRow, i - beg);
1553 +            if (modCount != expectedModCount)
1554 +                throw new ConcurrentModificationException();
1555 +            expectedModCount++;
1556 +            modCount++;
1557 +            int w = beg;
1558 +            for (i = beg; i < end; i++)
1559 +                if (isClear(deathRow, i - beg))
1560 +                    es[w++] = es[i];
1561 +            final int oldSize = size;
1562 +            System.arraycopy(es, end, es, w, oldSize - end);
1563 +            Arrays.fill(es, size -= (end - w), oldSize, null);
1564 +            // checkInvariants();
1565 +            return true;
1566 +        } else {
1567 +            if (modCount != expectedModCount)
1568 +                throw new ConcurrentModificationException();
1569 +            // checkInvariants();
1570 +            return false;
1571 +        }
1572 +    }
1573 +
1574 +    @Override
1575 +    public void replaceAll(UnaryOperator<E> operator) {
1576 +        Objects.requireNonNull(operator);
1577 +        final int expectedModCount = modCount;
1578 +        final Object[] es = elementData;
1579 +        final int size = this.size;
1580 +        for (int i = 0; modCount == expectedModCount && i < size; i++)
1581 +            es[i] = operator.apply(elementAt(es, i));
1582 +        if (modCount != expectedModCount)
1583 +            throw new ConcurrentModificationException();
1584 +        modCount++;
1585 +        // checkInvariants();
1586 +    }
1587 +
1588 +    @Override
1589 +    @SuppressWarnings("unchecked")
1590 +    public void sort(Comparator<? super E> c) {
1591 +        final int expectedModCount = modCount;
1592 +        Arrays.sort((E[]) elementData, 0, size, c);
1593 +        if (modCount != expectedModCount)
1594 +            throw new ConcurrentModificationException();
1595 +        modCount++;
1596 +        // checkInvariants();
1597 +    }
1598 +
1599 +    void checkInvariants() {
1600 +        // assert size >= 0;
1601 +        // assert size == elementData.length || elementData[size] == null;
1602      }
1603   }

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