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Comparing jsr166/src/main/java/util/ArrayList.java (file contents):
Revision 1.30 by jsr166, Sun Sep 5 21:32:19 2010 UTC vs.
Revision 1.38 by jsr166, Sat Nov 12 20:51:59 2016 UTC

# Line 1 | Line 1
1   /*
2 < * Copyright (c) 1997, 2008, Oracle and/or its affiliates. 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 25 | Line 25
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 <            int newCapacity = (oldCapacity * 3)/2 + 1;
216 <            if (newCapacity < minCapacity)
184 <                newCapacity = minCapacity;
185 <            // minCapacity is usually close to size, so this is a win:
186 <            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 197 | 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 221 | 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 241 | 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 259 | 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")
270 <                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 306 | 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 345 | Line 431 | public class ArrayList<E> extends Abstra
431       * @throws IndexOutOfBoundsException {@inheritDoc}
432       */
433      public E get(int index) {
434 <        rangeCheck(index);
349 <
434 >        Objects.checkIndex(index, size);
435          return elementData(index);
436      }
437  
# Line 360 | Line 445 | public class ArrayList<E> extends Abstra
445       * @throws IndexOutOfBoundsException {@inheritDoc}
446       */
447      public E set(int index, E element) {
448 <        rangeCheck(index);
364 <
448 >        Objects.checkIndex(index, size);
449          E oldValue = elementData(index);
450          elementData[index] = element;
451          return oldValue;
452      }
453  
454      /**
455 +     * This helper method split out from add(E) to keep method
456 +     * bytecode size under 35 (the -XX:MaxInlineSize default value),
457 +     * which helps when add(E) is called in a C1-compiled loop.
458 +     */
459 +    private void add(E e, Object[] elementData, int s) {
460 +        if (s == elementData.length)
461 +            elementData = grow();
462 +        elementData[s] = e;
463 +        size = s + 1;
464 +    }
465 +
466 +    /**
467       * Appends the specified element to the end of this list.
468       *
469       * @param e element to be appended to this list
470 <     * @return <tt>true</tt> (as specified by {@link Collection#add})
470 >     * @return {@code true} (as specified by {@link Collection#add})
471       */
472      public boolean add(E e) {
473 <        ensureCapacity(size + 1);  // Increments modCount!!
474 <        elementData[size++] = e;
473 >        modCount++;
474 >        add(e, elementData, size);
475          return true;
476      }
477  
# Line 390 | Line 486 | public class ArrayList<E> extends Abstra
486       */
487      public void add(int index, E element) {
488          rangeCheckForAdd(index);
489 <
490 <        ensureCapacity(size+1);  // Increments modCount!!
491 <        System.arraycopy(elementData, index, elementData, index + 1,
492 <                         size - index);
489 >        modCount++;
490 >        final int s;
491 >        Object[] elementData;
492 >        if ((s = size) == (elementData = this.elementData).length)
493 >            elementData = grow();
494 >        System.arraycopy(elementData, index,
495 >                         elementData, index + 1,
496 >                         s - index);
497          elementData[index] = element;
498 <        size++;
498 >        size = s + 1;
499      }
500  
501      /**
# Line 408 | Line 508 | public class ArrayList<E> extends Abstra
508       * @throws IndexOutOfBoundsException {@inheritDoc}
509       */
510      public E remove(int index) {
511 <        rangeCheck(index);
511 >        Objects.checkIndex(index, size);
512  
513          modCount++;
514          E oldValue = elementData(index);
# Line 417 | Line 517 | public class ArrayList<E> extends Abstra
517          if (numMoved > 0)
518              System.arraycopy(elementData, index+1, elementData, index,
519                               numMoved);
520 <        elementData[--size] = null; // Let gc do its work
520 >        elementData[--size] = null; // clear to let GC do its work
521  
522          return oldValue;
523      }
# Line 426 | Line 526 | public class ArrayList<E> extends Abstra
526       * Removes the first occurrence of the specified element from this list,
527       * if it is present.  If the list does not contain the element, it is
528       * unchanged.  More formally, removes the element with the lowest index
529 <     * <tt>i</tt> such that
530 <     * <tt>(o==null&nbsp;?&nbsp;get(i)==null&nbsp;:&nbsp;o.equals(get(i)))</tt>
531 <     * (if such an element exists).  Returns <tt>true</tt> if this list
529 >     * {@code i} such that
530 >     * {@code Objects.equals(o, get(i))}
531 >     * (if such an element exists).  Returns {@code true} if this list
532       * contained the specified element (or equivalently, if this list
533       * changed as a result of the call).
534       *
535       * @param o element to be removed from this list, if present
536 <     * @return <tt>true</tt> if this list contained the specified element
536 >     * @return {@code true} if this list contained the specified element
537       */
538      public boolean remove(Object o) {
539          if (o == null) {
# Line 462 | Line 562 | public class ArrayList<E> extends Abstra
562          if (numMoved > 0)
563              System.arraycopy(elementData, index+1, elementData, index,
564                               numMoved);
565 <        elementData[--size] = null; // Let gc do its work
565 >        elementData[--size] = null; // clear to let GC do its work
566      }
567  
568      /**
# Line 472 | Line 572 | public class ArrayList<E> extends Abstra
572      public void clear() {
573          modCount++;
574  
575 <        // Let gc do its work
575 >        // clear to let GC do its work
576          for (int i = 0; i < size; i++)
577              elementData[i] = null;
578  
# Line 489 | Line 589 | public class ArrayList<E> extends Abstra
589       * list is nonempty.)
590       *
591       * @param c collection containing elements to be added to this list
592 <     * @return <tt>true</tt> if this list changed as a result of the call
592 >     * @return {@code true} if this list changed as a result of the call
593       * @throws NullPointerException if the specified collection is null
594       */
595      public boolean addAll(Collection<? extends E> c) {
596          Object[] a = c.toArray();
597 +        modCount++;
598          int numNew = a.length;
599 <        ensureCapacity(size + numNew);  // Increments modCount
600 <        System.arraycopy(a, 0, elementData, size, numNew);
601 <        size += numNew;
602 <        return numNew != 0;
599 >        if (numNew == 0)
600 >            return false;
601 >        Object[] elementData;
602 >        final int s;
603 >        if (numNew > (elementData = this.elementData).length - (s = size))
604 >            elementData = grow(s + numNew);
605 >        System.arraycopy(a, 0, elementData, s, numNew);
606 >        size = s + numNew;
607 >        return true;
608      }
609  
610      /**
# Line 512 | Line 618 | public class ArrayList<E> extends Abstra
618       * @param index index at which to insert the first element from the
619       *              specified collection
620       * @param c collection containing elements to be added to this list
621 <     * @return <tt>true</tt> if this list changed as a result of the call
621 >     * @return {@code true} if this list changed as a result of the call
622       * @throws IndexOutOfBoundsException {@inheritDoc}
623       * @throws NullPointerException if the specified collection is null
624       */
# Line 520 | Line 626 | public class ArrayList<E> extends Abstra
626          rangeCheckForAdd(index);
627  
628          Object[] a = c.toArray();
629 +        modCount++;
630          int numNew = a.length;
631 <        ensureCapacity(size + numNew);  // Increments modCount
631 >        if (numNew == 0)
632 >            return false;
633 >        Object[] elementData;
634 >        final int s;
635 >        if (numNew > (elementData = this.elementData).length - (s = size))
636 >            elementData = grow(s + numNew);
637  
638 <        int numMoved = size - index;
638 >        int numMoved = s - index;
639          if (numMoved > 0)
640 <            System.arraycopy(elementData, index, elementData, index + numNew,
640 >            System.arraycopy(elementData, index,
641 >                             elementData, index + numNew,
642                               numMoved);
530
643          System.arraycopy(a, 0, elementData, index, numNew);
644 <        size += numNew;
645 <        return numNew != 0;
644 >        size = s + numNew;
645 >        return true;
646      }
647  
648      /**
# Line 543 | Line 655 | public class ArrayList<E> extends Abstra
655       * @throws IndexOutOfBoundsException if {@code fromIndex} or
656       *         {@code toIndex} is out of range
657       *         ({@code fromIndex < 0 ||
546     *          fromIndex >= size() ||
658       *          toIndex > size() ||
659       *          toIndex < fromIndex})
660       */
661      protected void removeRange(int fromIndex, int toIndex) {
662 +        if (fromIndex > toIndex) {
663 +            throw new IndexOutOfBoundsException(
664 +                    outOfBoundsMsg(fromIndex, toIndex));
665 +        }
666          modCount++;
667          int numMoved = size - toIndex;
668          System.arraycopy(elementData, toIndex, elementData, fromIndex,
669                           numMoved);
670  
671 <        // Let gc do its work
671 >        // clear to let GC do its work
672          int newSize = size - (toIndex-fromIndex);
673 <        while (size != newSize)
674 <            elementData[--size] = null;
675 <    }
676 <
562 <    /**
563 <     * Checks if the given index is in range.  If not, throws an appropriate
564 <     * runtime exception.  This method does *not* check if the index is
565 <     * negative: It is always used immediately prior to an array access,
566 <     * which throws an ArrayIndexOutOfBoundsException if index is negative.
567 <     */
568 <    private void rangeCheck(int index) {
569 <        if (index >= size)
570 <            throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
673 >        for (int i = newSize; i < size; i++) {
674 >            elementData[i] = null;
675 >        }
676 >        size = newSize;
677      }
678  
679      /**
# Line 588 | 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       */
# Line 612 | 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       */
# Line 623 | Line 740 | public class ArrayList<E> extends Abstra
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);
743 >        Objects.requireNonNull(c);
744 >        final Object[] es = elementData;
745 >        final int size = this.size;
746 >        final boolean modified;
747 >        int r;
748 >        // Optimize for initial run of survivors
749 >        for (r = 0; r < size && c.contains(es[r]) == complement; r++)
750 >            ;
751 >        if (modified = (r < size)) {
752 >            int w = r++;
753 >            try {
754 >                for (Object e; r < size; 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, size - r);
761                  w += size - r;
762 <            }
763 <            if (w != size) {
643 <                for (int i = w; i < size; i++)
644 <                    elementData[i] = null;
762 >                throw ex;
763 >            } finally {
764                  modCount += size - w;
765 <                size = w;
647 <                modified = true;
765 >                Arrays.fill(es, (this.size = w), size, null);
766              }
767          }
768          return modified;
769      }
770  
771      /**
772 <     * Save the state of the <tt>ArrayList</tt> instance to a stream (that
772 >     * Save the state of the {@code ArrayList} instance to a stream (that
773       * is, serialize it).
774       *
775 <     * @serialData The length of the array backing the <tt>ArrayList</tt>
775 >     * @serialData The length of the array backing the {@code ArrayList}
776       *             instance is emitted (int), followed by all of its elements
777 <     *             (each an <tt>Object</tt>) in the proper order.
777 >     *             (each an {@code Object}) in the proper order.
778       */
779      private void writeObject(java.io.ObjectOutputStream s)
780          throws java.io.IOException{
# Line 664 | Line 782 | public class ArrayList<E> extends Abstra
782          int expectedModCount = modCount;
783          s.defaultWriteObject();
784  
785 <        // Write out array length
786 <        s.writeInt(elementData.length);
785 >        // Write out size as capacity for behavioural compatibility with clone()
786 >        s.writeInt(size);
787  
788          // Write out all elements in the proper order.
789 <        for (int i=0; i<size; i++)
789 >        for (int i=0; i<size; i++) {
790              s.writeObject(elementData[i]);
791 +        }
792  
793          if (modCount != expectedModCount) {
794              throw new ConcurrentModificationException();
795          }
677
796      }
797  
798      /**
799 <     * Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
799 >     * Reconstitute the {@code ArrayList} instance from a stream (that is,
800       * deserialize it).
801       */
802      private void readObject(java.io.ObjectInputStream s)
803          throws java.io.IOException, ClassNotFoundException {
804 +
805          // Read in size, and any hidden stuff
806          s.defaultReadObject();
807  
808 <        // Read in array length and allocate array
809 <        int arrayLength = s.readInt();
810 <        Object[] a = elementData = new Object[arrayLength];
811 <
812 <        // Read in all elements in the proper order.
813 <        for (int i=0; i<size; i++)
814 <            a[i] = s.readObject();
808 >        // Read in capacity
809 >        s.readInt(); // ignored
810 >
811 >        if (size > 0) {
812 >            // like clone(), allocate array based upon size not capacity
813 >            Object[] elements = new Object[size];
814 >
815 >            // Read in all elements in the proper order.
816 >            for (int i = 0; i < size; i++) {
817 >                elements[i] = s.readObject();
818 >            }
819 >
820 >            elementData = elements;
821 >        } else if (size == 0) {
822 >            elementData = EMPTY_ELEMENTDATA;
823 >        } else {
824 >            throw new java.io.InvalidObjectException("Invalid size: " + size);
825 >        }
826      }
827  
828      /**
# Line 708 | Line 838 | public class ArrayList<E> extends Abstra
838       * @throws IndexOutOfBoundsException {@inheritDoc}
839       */
840      public ListIterator<E> listIterator(int index) {
841 <        if (index < 0 || index > size)
712 <            throw new IndexOutOfBoundsException("Index: "+index);
841 >        rangeCheckForAdd(index);
842          return new ListItr(index);
843      }
844  
# Line 744 | Line 873 | public class ArrayList<E> extends Abstra
873          int lastRet = -1; // index of last element returned; -1 if no such
874          int expectedModCount = modCount;
875  
876 +        // prevent creating a synthetic constructor
877 +        Itr() {}
878 +
879          public boolean hasNext() {
880              return cursor != size;
881          }
# Line 776 | Line 908 | public class ArrayList<E> extends Abstra
908              }
909          }
910  
911 +        @Override
912 +        @SuppressWarnings("unchecked")
913 +        public void forEachRemaining(Consumer<? super E> consumer) {
914 +            Objects.requireNonNull(consumer);
915 +            final int size = ArrayList.this.size;
916 +            int i = cursor;
917 +            if (i >= size) {
918 +                return;
919 +            }
920 +            final Object[] elementData = ArrayList.this.elementData;
921 +            if (i >= elementData.length) {
922 +                throw new ConcurrentModificationException();
923 +            }
924 +            while (i != size && modCount == expectedModCount) {
925 +                consumer.accept((E) elementData[i++]);
926 +            }
927 +            // update once at end of iteration to reduce heap write traffic
928 +            cursor = i;
929 +            lastRet = i - 1;
930 +            checkForComodification();
931 +        }
932 +
933          final void checkForComodification() {
934              if (modCount != expectedModCount)
935                  throw new ConcurrentModificationException();
# Line 874 | Line 1028 | public class ArrayList<E> extends Abstra
1028       */
1029      public List<E> subList(int fromIndex, int toIndex) {
1030          subListRangeCheck(fromIndex, toIndex, size);
1031 <        return new SubList(this, 0, fromIndex, toIndex);
1031 >        return new SubList<>(this, fromIndex, toIndex);
1032      }
1033  
1034 <    static void subListRangeCheck(int fromIndex, int toIndex, int size) {
1035 <        if (fromIndex < 0)
1036 <            throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
883 <        if (toIndex > size)
884 <            throw new IndexOutOfBoundsException("toIndex = " + toIndex);
885 <        if (fromIndex > toIndex)
886 <            throw new IllegalArgumentException("fromIndex(" + fromIndex +
887 <                                               ") > toIndex(" + toIndex + ")");
888 <    }
889 <
890 <    private class SubList extends AbstractList<E> implements RandomAccess {
891 <        private final AbstractList<E> parent;
892 <        private final int parentOffset;
1034 >    private static class SubList<E> extends AbstractList<E> implements RandomAccess {
1035 >        private final ArrayList<E> root;
1036 >        private final SubList<E> parent;
1037          private final int offset;
1038 <        int size;
1038 >        private int size;
1039 >
1040 >        /**
1041 >         * Constructs a sublist of an arbitrary ArrayList.
1042 >         */
1043 >        public SubList(ArrayList<E> root, int fromIndex, int toIndex) {
1044 >            this.root = root;
1045 >            this.parent = null;
1046 >            this.offset = fromIndex;
1047 >            this.size = toIndex - fromIndex;
1048 >            this.modCount = root.modCount;
1049 >        }
1050  
1051 <        SubList(AbstractList<E> parent,
1052 <                int offset, int fromIndex, int toIndex) {
1051 >        /**
1052 >         * Constructs a sublist of another SubList.
1053 >         */
1054 >        private SubList(SubList<E> parent, int fromIndex, int toIndex) {
1055 >            this.root = parent.root;
1056              this.parent = parent;
1057 <            this.parentOffset = fromIndex;
900 <            this.offset = offset + fromIndex;
1057 >            this.offset = parent.offset + fromIndex;
1058              this.size = toIndex - fromIndex;
1059 <            this.modCount = ArrayList.this.modCount;
1059 >            this.modCount = root.modCount;
1060          }
1061  
1062 <        public E set(int index, E e) {
1063 <            rangeCheck(index);
1062 >        public E set(int index, E element) {
1063 >            Objects.checkIndex(index, size);
1064              checkForComodification();
1065 <            E oldValue = ArrayList.this.elementData(offset + index);
1066 <            ArrayList.this.elementData[offset + index] = e;
1065 >            E oldValue = root.elementData(offset + index);
1066 >            root.elementData[offset + index] = element;
1067              return oldValue;
1068          }
1069  
1070          public E get(int index) {
1071 <            rangeCheck(index);
1071 >            Objects.checkIndex(index, size);
1072              checkForComodification();
1073 <            return ArrayList.this.elementData(offset + index);
1073 >            return root.elementData(offset + index);
1074          }
1075  
1076          public int size() {
1077              checkForComodification();
1078 <            return this.size;
1078 >            return size;
1079          }
1080  
1081 <        public void add(int index, E e) {
1081 >        public void add(int index, E element) {
1082              rangeCheckForAdd(index);
1083              checkForComodification();
1084 <            parent.add(parentOffset + index, e);
1085 <            this.modCount = parent.modCount;
929 <            this.size++;
1084 >            root.add(offset + index, element);
1085 >            updateSizeAndModCount(1);
1086          }
1087  
1088          public E remove(int index) {
1089 <            rangeCheck(index);
1089 >            Objects.checkIndex(index, size);
1090              checkForComodification();
1091 <            E result = parent.remove(parentOffset + index);
1092 <            this.modCount = parent.modCount;
937 <            this.size--;
1091 >            E result = root.remove(offset + index);
1092 >            updateSizeAndModCount(-1);
1093              return result;
1094          }
1095  
1096          protected void removeRange(int fromIndex, int toIndex) {
1097              checkForComodification();
1098 <            parent.removeRange(parentOffset + fromIndex,
1099 <                               parentOffset + toIndex);
945 <            this.modCount = parent.modCount;
946 <            this.size -= toIndex - fromIndex;
1098 >            root.removeRange(offset + fromIndex, offset + toIndex);
1099 >            updateSizeAndModCount(fromIndex - toIndex);
1100          }
1101  
1102          public boolean addAll(Collection<? extends E> c) {
# Line 955 | Line 1108 | public class ArrayList<E> extends Abstra
1108              int cSize = c.size();
1109              if (cSize==0)
1110                  return false;
958
1111              checkForComodification();
1112 <            parent.addAll(parentOffset + index, c);
1113 <            this.modCount = parent.modCount;
962 <            this.size += cSize;
1112 >            root.addAll(offset + index, c);
1113 >            updateSizeAndModCount(cSize);
1114              return true;
1115          }
1116  
# Line 967 | Line 1118 | public class ArrayList<E> extends Abstra
1118              return listIterator();
1119          }
1120  
1121 <        public ListIterator<E> listIterator(final int index) {
1121 >        public ListIterator<E> listIterator(int index) {
1122              checkForComodification();
1123              rangeCheckForAdd(index);
973            final int offset = this.offset;
1124  
1125              return new ListIterator<E>() {
1126                  int cursor = index;
1127                  int lastRet = -1;
1128 <                int expectedModCount = ArrayList.this.modCount;
1128 >                int expectedModCount = root.modCount;
1129  
1130                  public boolean hasNext() {
1131                      return cursor != SubList.this.size;
# Line 987 | Line 1137 | public class ArrayList<E> extends Abstra
1137                      int i = cursor;
1138                      if (i >= SubList.this.size)
1139                          throw new NoSuchElementException();
1140 <                    Object[] elementData = ArrayList.this.elementData;
1140 >                    Object[] elementData = root.elementData;
1141                      if (offset + i >= elementData.length)
1142                          throw new ConcurrentModificationException();
1143                      cursor = i + 1;
# Line 1004 | Line 1154 | public class ArrayList<E> extends Abstra
1154                      int i = cursor - 1;
1155                      if (i < 0)
1156                          throw new NoSuchElementException();
1157 <                    Object[] elementData = ArrayList.this.elementData;
1157 >                    Object[] elementData = root.elementData;
1158                      if (offset + i >= elementData.length)
1159                          throw new ConcurrentModificationException();
1160                      cursor = i;
1161                      return (E) elementData[offset + (lastRet = i)];
1162                  }
1163  
1164 +                @SuppressWarnings("unchecked")
1165 +                public void forEachRemaining(Consumer<? super E> consumer) {
1166 +                    Objects.requireNonNull(consumer);
1167 +                    final int size = SubList.this.size;
1168 +                    int i = cursor;
1169 +                    if (i >= size) {
1170 +                        return;
1171 +                    }
1172 +                    final Object[] elementData = root.elementData;
1173 +                    if (offset + i >= elementData.length) {
1174 +                        throw new ConcurrentModificationException();
1175 +                    }
1176 +                    while (i != size && modCount == expectedModCount) {
1177 +                        consumer.accept((E) elementData[offset + (i++)]);
1178 +                    }
1179 +                    // update once at end of iteration to reduce heap write traffic
1180 +                    lastRet = cursor = i;
1181 +                    checkForComodification();
1182 +                }
1183 +
1184                  public int nextIndex() {
1185                      return cursor;
1186                  }
# Line 1028 | Line 1198 | public class ArrayList<E> extends Abstra
1198                          SubList.this.remove(lastRet);
1199                          cursor = lastRet;
1200                          lastRet = -1;
1201 <                        expectedModCount = ArrayList.this.modCount;
1201 >                        expectedModCount = root.modCount;
1202                      } catch (IndexOutOfBoundsException ex) {
1203                          throw new ConcurrentModificationException();
1204                      }
# Line 1040 | Line 1210 | public class ArrayList<E> extends Abstra
1210                      checkForComodification();
1211  
1212                      try {
1213 <                        ArrayList.this.set(offset + lastRet, e);
1213 >                        root.set(offset + lastRet, e);
1214                      } catch (IndexOutOfBoundsException ex) {
1215                          throw new ConcurrentModificationException();
1216                      }
# Line 1054 | Line 1224 | public class ArrayList<E> extends Abstra
1224                          SubList.this.add(i, e);
1225                          cursor = i + 1;
1226                          lastRet = -1;
1227 <                        expectedModCount = ArrayList.this.modCount;
1227 >                        expectedModCount = root.modCount;
1228                      } catch (IndexOutOfBoundsException ex) {
1229                          throw new ConcurrentModificationException();
1230                      }
1231                  }
1232  
1233                  final void checkForComodification() {
1234 <                    if (expectedModCount != ArrayList.this.modCount)
1234 >                    if (root.modCount != expectedModCount)
1235                          throw new ConcurrentModificationException();
1236                  }
1237              };
# Line 1069 | Line 1239 | public class ArrayList<E> extends Abstra
1239  
1240          public List<E> subList(int fromIndex, int toIndex) {
1241              subListRangeCheck(fromIndex, toIndex, size);
1242 <            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));
1242 >            return new SubList<>(this, fromIndex, toIndex);
1243          }
1244  
1245          private void rangeCheckForAdd(int index) {
# Line 1087 | Line 1252 | public class ArrayList<E> extends Abstra
1252          }
1253  
1254          private void checkForComodification() {
1255 <            if (ArrayList.this.modCount != this.modCount)
1255 >            if (root.modCount != modCount)
1256                  throw new ConcurrentModificationException();
1257          }
1258 +
1259 +        private void updateSizeAndModCount(int sizeChange) {
1260 +            SubList<E> slist = this;
1261 +            do {
1262 +                slist.size += sizeChange;
1263 +                slist.modCount = root.modCount;
1264 +                slist = slist.parent;
1265 +            } while (slist != null);
1266 +        }
1267 +
1268 +        public Spliterator<E> spliterator() {
1269 +            checkForComodification();
1270 +
1271 +            // ArrayListSpliterator is not used because late-binding logic
1272 +            // is different here
1273 +            return new Spliterator<>() {
1274 +                private int index = offset; // current index, modified on advance/split
1275 +                private int fence = -1; // -1 until used; then one past last index
1276 +                private int expectedModCount; // initialized when fence set
1277 +
1278 +                private int getFence() { // initialize fence to size on first use
1279 +                    int hi; // (a specialized variant appears in method forEach)
1280 +                    if ((hi = fence) < 0) {
1281 +                        expectedModCount = modCount;
1282 +                        hi = fence = offset + size;
1283 +                    }
1284 +                    return hi;
1285 +                }
1286 +
1287 +                public ArrayListSpliterator<E> trySplit() {
1288 +                    int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1289 +                    // ArrayListSpliterator could be used here as the source is already bound
1290 +                    return (lo >= mid) ? null : // divide range in half unless too small
1291 +                        new ArrayListSpliterator<>(root, lo, index = mid,
1292 +                                                   expectedModCount);
1293 +                }
1294 +
1295 +                public boolean tryAdvance(Consumer<? super E> action) {
1296 +                    Objects.requireNonNull(action);
1297 +                    int hi = getFence(), i = index;
1298 +                    if (i < hi) {
1299 +                        index = i + 1;
1300 +                        @SuppressWarnings("unchecked") E e = (E)root.elementData[i];
1301 +                        action.accept(e);
1302 +                        if (root.modCount != expectedModCount)
1303 +                            throw new ConcurrentModificationException();
1304 +                        return true;
1305 +                    }
1306 +                    return false;
1307 +                }
1308 +
1309 +                public void forEachRemaining(Consumer<? super E> action) {
1310 +                    Objects.requireNonNull(action);
1311 +                    int i, hi, mc; // hoist accesses and checks from loop
1312 +                    ArrayList<E> lst = root;
1313 +                    Object[] a;
1314 +                    if ((a = lst.elementData) != null) {
1315 +                        if ((hi = fence) < 0) {
1316 +                            mc = modCount;
1317 +                            hi = offset + size;
1318 +                        }
1319 +                        else
1320 +                            mc = expectedModCount;
1321 +                        if ((i = index) >= 0 && (index = hi) <= a.length) {
1322 +                            for (; i < hi; ++i) {
1323 +                                @SuppressWarnings("unchecked") E e = (E) a[i];
1324 +                                action.accept(e);
1325 +                            }
1326 +                            if (lst.modCount == mc)
1327 +                                return;
1328 +                        }
1329 +                    }
1330 +                    throw new ConcurrentModificationException();
1331 +                }
1332 +
1333 +                public long estimateSize() {
1334 +                    return (long) (getFence() - index);
1335 +                }
1336 +
1337 +                public int characteristics() {
1338 +                    return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
1339 +                }
1340 +            };
1341 +        }
1342 +    }
1343 +
1344 +    @Override
1345 +    public void forEach(Consumer<? super E> action) {
1346 +        Objects.requireNonNull(action);
1347 +        final int expectedModCount = modCount;
1348 +        @SuppressWarnings("unchecked")
1349 +        final E[] elementData = (E[]) this.elementData;
1350 +        final int size = this.size;
1351 +        for (int i=0; modCount == expectedModCount && i < size; i++) {
1352 +            action.accept(elementData[i]);
1353 +        }
1354 +        if (modCount != expectedModCount) {
1355 +            throw new ConcurrentModificationException();
1356 +        }
1357 +    }
1358 +
1359 +    /**
1360 +     * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
1361 +     * and <em>fail-fast</em> {@link Spliterator} over the elements in this
1362 +     * list.
1363 +     *
1364 +     * <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
1365 +     * {@link Spliterator#SUBSIZED}, and {@link Spliterator#ORDERED}.
1366 +     * Overriding implementations should document the reporting of additional
1367 +     * characteristic values.
1368 +     *
1369 +     * @return a {@code Spliterator} over the elements in this list
1370 +     * @since 1.8
1371 +     */
1372 +    @Override
1373 +    public Spliterator<E> spliterator() {
1374 +        return new ArrayListSpliterator<>(this, 0, -1, 0);
1375 +    }
1376 +
1377 +    /** Index-based split-by-two, lazily initialized Spliterator */
1378 +    static final class ArrayListSpliterator<E> implements Spliterator<E> {
1379 +
1380 +        /*
1381 +         * If ArrayLists were immutable, or structurally immutable (no
1382 +         * adds, removes, etc), we could implement their spliterators
1383 +         * with Arrays.spliterator. Instead we detect as much
1384 +         * interference during traversal as practical without
1385 +         * sacrificing much performance. We rely primarily on
1386 +         * modCounts. These are not guaranteed to detect concurrency
1387 +         * violations, and are sometimes overly conservative about
1388 +         * within-thread interference, but detect enough problems to
1389 +         * be worthwhile in practice. To carry this out, we (1) lazily
1390 +         * initialize fence and expectedModCount until the latest
1391 +         * point that we need to commit to the state we are checking
1392 +         * against; thus improving precision.  (This doesn't apply to
1393 +         * SubLists, that create spliterators with current non-lazy
1394 +         * values).  (2) We perform only a single
1395 +         * ConcurrentModificationException check at the end of forEach
1396 +         * (the most performance-sensitive method). When using forEach
1397 +         * (as opposed to iterators), we can normally only detect
1398 +         * interference after actions, not before. Further
1399 +         * CME-triggering checks apply to all other possible
1400 +         * violations of assumptions for example null or too-small
1401 +         * elementData array given its size(), that could only have
1402 +         * occurred due to interference.  This allows the inner loop
1403 +         * of forEach to run without any further checks, and
1404 +         * simplifies lambda-resolution. While this does entail a
1405 +         * number of checks, note that in the common case of
1406 +         * list.stream().forEach(a), no checks or other computation
1407 +         * occur anywhere other than inside forEach itself.  The other
1408 +         * less-often-used methods cannot take advantage of most of
1409 +         * these streamlinings.
1410 +         */
1411 +
1412 +        private final ArrayList<E> list;
1413 +        private int index; // current index, modified on advance/split
1414 +        private int fence; // -1 until used; then one past last index
1415 +        private int expectedModCount; // initialized when fence set
1416 +
1417 +        /** Create new spliterator covering the given  range */
1418 +        ArrayListSpliterator(ArrayList<E> list, int origin, int fence,
1419 +                             int expectedModCount) {
1420 +            this.list = list; // OK if null unless traversed
1421 +            this.index = origin;
1422 +            this.fence = fence;
1423 +            this.expectedModCount = expectedModCount;
1424 +        }
1425 +
1426 +        private int getFence() { // initialize fence to size on first use
1427 +            int hi; // (a specialized variant appears in method forEach)
1428 +            ArrayList<E> lst;
1429 +            if ((hi = fence) < 0) {
1430 +                if ((lst = list) == null)
1431 +                    hi = fence = 0;
1432 +                else {
1433 +                    expectedModCount = lst.modCount;
1434 +                    hi = fence = lst.size;
1435 +                }
1436 +            }
1437 +            return hi;
1438 +        }
1439 +
1440 +        public ArrayListSpliterator<E> trySplit() {
1441 +            int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1442 +            return (lo >= mid) ? null : // divide range in half unless too small
1443 +                new ArrayListSpliterator<>(list, lo, index = mid,
1444 +                                           expectedModCount);
1445 +        }
1446 +
1447 +        public boolean tryAdvance(Consumer<? super E> action) {
1448 +            if (action == null)
1449 +                throw new NullPointerException();
1450 +            int hi = getFence(), i = index;
1451 +            if (i < hi) {
1452 +                index = i + 1;
1453 +                @SuppressWarnings("unchecked") E e = (E)list.elementData[i];
1454 +                action.accept(e);
1455 +                if (list.modCount != expectedModCount)
1456 +                    throw new ConcurrentModificationException();
1457 +                return true;
1458 +            }
1459 +            return false;
1460 +        }
1461 +
1462 +        public void forEachRemaining(Consumer<? super E> action) {
1463 +            int i, hi, mc; // hoist accesses and checks from loop
1464 +            ArrayList<E> lst; Object[] a;
1465 +            if (action == null)
1466 +                throw new NullPointerException();
1467 +            if ((lst = list) != null && (a = lst.elementData) != null) {
1468 +                if ((hi = fence) < 0) {
1469 +                    mc = lst.modCount;
1470 +                    hi = lst.size;
1471 +                }
1472 +                else
1473 +                    mc = expectedModCount;
1474 +                if ((i = index) >= 0 && (index = hi) <= a.length) {
1475 +                    for (; i < hi; ++i) {
1476 +                        @SuppressWarnings("unchecked") E e = (E) a[i];
1477 +                        action.accept(e);
1478 +                    }
1479 +                    if (lst.modCount == mc)
1480 +                        return;
1481 +                }
1482 +            }
1483 +            throw new ConcurrentModificationException();
1484 +        }
1485 +
1486 +        public long estimateSize() {
1487 +            return (long) (getFence() - index);
1488 +        }
1489 +
1490 +        public int characteristics() {
1491 +            return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
1492 +        }
1493 +    }
1494 +
1495 +    @SuppressWarnings("unchecked")
1496 +    @Override
1497 +    public boolean removeIf(Predicate<? super E> filter) {
1498 +        Objects.requireNonNull(filter);
1499 +        int expectedModCount = modCount;
1500 +        final Object[] es = elementData;
1501 +        final int size = this.size;
1502 +        final boolean modified;
1503 +        int r;
1504 +        // Optimize for initial run of survivors
1505 +        for (r = 0; r < size && !filter.test((E) es[r]); r++)
1506 +            ;
1507 +        if (modified = (r < size)) {
1508 +            expectedModCount++;
1509 +            modCount++;
1510 +            int w = r++;
1511 +            try {
1512 +                for (E e; r < size; r++)
1513 +                    if (!filter.test(e = (E) es[r]))
1514 +                        es[w++] = e;
1515 +            } catch (Throwable ex) {
1516 +                // copy remaining elements
1517 +                System.arraycopy(es, r, es, w, size - r);
1518 +                w += size - r;
1519 +                throw ex;
1520 +            } finally {
1521 +                Arrays.fill(es, (this.size = w), size, null);
1522 +            }
1523 +        }
1524 +        if (modCount != expectedModCount)
1525 +            throw new ConcurrentModificationException();
1526 +        return modified;
1527 +    }
1528 +
1529 +    @Override
1530 +    @SuppressWarnings("unchecked")
1531 +    public void replaceAll(UnaryOperator<E> operator) {
1532 +        Objects.requireNonNull(operator);
1533 +        final int expectedModCount = modCount;
1534 +        final int size = this.size;
1535 +        for (int i=0; modCount == expectedModCount && i < size; i++) {
1536 +            elementData[i] = operator.apply((E) elementData[i]);
1537 +        }
1538 +        if (modCount != expectedModCount) {
1539 +            throw new ConcurrentModificationException();
1540 +        }
1541 +        modCount++;
1542 +    }
1543 +
1544 +    @Override
1545 +    @SuppressWarnings("unchecked")
1546 +    public void sort(Comparator<? super E> c) {
1547 +        final int expectedModCount = modCount;
1548 +        Arrays.sort((E[]) elementData, 0, size, c);
1549 +        if (modCount != expectedModCount) {
1550 +            throw new ConcurrentModificationException();
1551 +        }
1552 +        modCount++;
1553      }
1554   }

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