001/*
002 * Copyright (C) 2007 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.collect;
018
019import static com.google.common.base.Preconditions.checkArgument;
020import static com.google.common.base.Preconditions.checkElementIndex;
021import static com.google.common.base.Preconditions.checkNotNull;
022import static com.google.common.base.Preconditions.checkPositionIndex;
023import static com.google.common.base.Preconditions.checkPositionIndexes;
024import static com.google.common.collect.CollectPreconditions.checkNonnegative;
025import static com.google.common.collect.ObjectArrays.checkElementsNotNull;
026import static com.google.common.collect.RegularImmutableList.EMPTY;
027
028import com.google.common.annotations.Beta;
029import com.google.common.annotations.GwtCompatible;
030import com.google.errorprone.annotations.CanIgnoreReturnValue;
031import java.io.InvalidObjectException;
032import java.io.ObjectInputStream;
033import java.io.Serializable;
034import java.util.Arrays;
035import java.util.Collection;
036import java.util.Collections;
037import java.util.Comparator;
038import java.util.Iterator;
039import java.util.List;
040import java.util.RandomAccess;
041import org.checkerframework.checker.nullness.compatqual.NullableDecl;
042
043/**
044 * A {@link List} whose contents will never change, with many other important properties detailed at
045 * {@link ImmutableCollection}.
046 *
047 * <p>See the Guava User Guide article on <a href=
048 * "https://github.com/google/guava/wiki/ImmutableCollectionsExplained"> immutable collections</a>.
049 *
050 * @see ImmutableMap
051 * @see ImmutableSet
052 * @author Kevin Bourrillion
053 * @since 2.0
054 */
055@GwtCompatible(serializable = true, emulated = true)
056@SuppressWarnings("serial") // we're overriding default serialization
057public abstract class ImmutableList<E> extends ImmutableCollection<E>
058    implements List<E>, RandomAccess {
059  /**
060   * Returns the empty immutable list. This list behaves and performs comparably to {@link
061   * Collections#emptyList}, and is preferable mainly for consistency and maintainability of your
062   * code.
063   */
064  // Casting to any type is safe because the list will never hold any elements.
065  @SuppressWarnings("unchecked")
066  public static <E> ImmutableList<E> of() {
067    return (ImmutableList<E>) EMPTY;
068  }
069
070  /**
071   * Returns an immutable list containing a single element. This list behaves and performs
072   * comparably to {@link Collections#singleton}, but will not accept a null element. It is
073   * preferable mainly for consistency and maintainability of your code.
074   *
075   * @throws NullPointerException if {@code element} is null
076   */
077  public static <E> ImmutableList<E> of(E element) {
078    return construct(element);
079  }
080
081  /**
082   * Returns an immutable list containing the given elements, in order.
083   *
084   * @throws NullPointerException if any element is null
085   */
086  public static <E> ImmutableList<E> of(E e1, E e2) {
087    return construct(e1, e2);
088  }
089
090  /**
091   * Returns an immutable list containing the given elements, in order.
092   *
093   * @throws NullPointerException if any element is null
094   */
095  public static <E> ImmutableList<E> of(E e1, E e2, E e3) {
096    return construct(e1, e2, e3);
097  }
098
099  /**
100   * Returns an immutable list containing the given elements, in order.
101   *
102   * @throws NullPointerException if any element is null
103   */
104  public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4) {
105    return construct(e1, e2, e3, e4);
106  }
107
108  /**
109   * Returns an immutable list containing the given elements, in order.
110   *
111   * @throws NullPointerException if any element is null
112   */
113  public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4, E e5) {
114    return construct(e1, e2, e3, e4, e5);
115  }
116
117  /**
118   * Returns an immutable list containing the given elements, in order.
119   *
120   * @throws NullPointerException if any element is null
121   */
122  public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4, E e5, E e6) {
123    return construct(e1, e2, e3, e4, e5, e6);
124  }
125
126  /**
127   * Returns an immutable list containing the given elements, in order.
128   *
129   * @throws NullPointerException if any element is null
130   */
131  public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7) {
132    return construct(e1, e2, e3, e4, e5, e6, e7);
133  }
134
135  /**
136   * Returns an immutable list containing the given elements, in order.
137   *
138   * @throws NullPointerException if any element is null
139   */
140  public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8) {
141    return construct(e1, e2, e3, e4, e5, e6, e7, e8);
142  }
143
144  /**
145   * Returns an immutable list containing the given elements, in order.
146   *
147   * @throws NullPointerException if any element is null
148   */
149  public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9) {
150    return construct(e1, e2, e3, e4, e5, e6, e7, e8, e9);
151  }
152
153  /**
154   * Returns an immutable list containing the given elements, in order.
155   *
156   * @throws NullPointerException if any element is null
157   */
158  public static <E> ImmutableList<E> of(
159      E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10) {
160    return construct(e1, e2, e3, e4, e5, e6, e7, e8, e9, e10);
161  }
162
163  /**
164   * Returns an immutable list containing the given elements, in order.
165   *
166   * @throws NullPointerException if any element is null
167   */
168  public static <E> ImmutableList<E> of(
169      E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10, E e11) {
170    return construct(e1, e2, e3, e4, e5, e6, e7, e8, e9, e10, e11);
171  }
172
173  // These go up to eleven. After that, you just get the varargs form, and
174  // whatever warnings might come along with it. :(
175
176  /**
177   * Returns an immutable list containing the given elements, in order.
178   *
179   * <p>The array {@code others} must not be longer than {@code Integer.MAX_VALUE - 12}.
180   *
181   * @throws NullPointerException if any element is null
182   * @since 3.0 (source-compatible since 2.0)
183   */
184  @SafeVarargs // For Eclipse. For internal javac we have disabled this pointless type of warning.
185  public static <E> ImmutableList<E> of(
186      E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10, E e11, E e12, E... others) {
187    checkArgument(
188        others.length <= Integer.MAX_VALUE - 12,
189        "the total number of elements must fit in an int");
190    Object[] array = new Object[12 + others.length];
191    array[0] = e1;
192    array[1] = e2;
193    array[2] = e3;
194    array[3] = e4;
195    array[4] = e5;
196    array[5] = e6;
197    array[6] = e7;
198    array[7] = e8;
199    array[8] = e9;
200    array[9] = e10;
201    array[10] = e11;
202    array[11] = e12;
203    System.arraycopy(others, 0, array, 12, others.length);
204    return construct(array);
205  }
206
207  /**
208   * Returns an immutable list containing the given elements, in order. If {@code elements} is a
209   * {@link Collection}, this method behaves exactly as {@link #copyOf(Collection)}; otherwise, it
210   * behaves exactly as {@code copyOf(elements.iterator()}.
211   *
212   * @throws NullPointerException if any of {@code elements} is null
213   */
214  public static <E> ImmutableList<E> copyOf(Iterable<? extends E> elements) {
215    checkNotNull(elements); // TODO(kevinb): is this here only for GWT?
216    return (elements instanceof Collection)
217        ? copyOf((Collection<? extends E>) elements)
218        : copyOf(elements.iterator());
219  }
220
221  /**
222   * Returns an immutable list containing the given elements, in order.
223   *
224   * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
225   * safe to do so. The exact circumstances under which a copy will or will not be performed are
226   * undocumented and subject to change.
227   *
228   * <p>Note that if {@code list} is a {@code List<String>}, then {@code ImmutableList.copyOf(list)}
229   * returns an {@code ImmutableList<String>} containing each of the strings in {@code list}, while
230   * ImmutableList.of(list)} returns an {@code ImmutableList<List<String>>} containing one element
231   * (the given list itself).
232   *
233   * <p>This method is safe to use even when {@code elements} is a synchronized or concurrent
234   * collection that is currently being modified by another thread.
235   *
236   * @throws NullPointerException if any of {@code elements} is null
237   */
238  public static <E> ImmutableList<E> copyOf(Collection<? extends E> elements) {
239    if (elements instanceof ImmutableCollection) {
240      @SuppressWarnings("unchecked") // all supported methods are covariant
241      ImmutableList<E> list = ((ImmutableCollection<E>) elements).asList();
242      return list.isPartialView() ? ImmutableList.<E>asImmutableList(list.toArray()) : list;
243    }
244    return construct(elements.toArray());
245  }
246
247  /**
248   * Returns an immutable list containing the given elements, in order.
249   *
250   * @throws NullPointerException if any of {@code elements} is null
251   */
252  public static <E> ImmutableList<E> copyOf(Iterator<? extends E> elements) {
253    // We special-case for 0 or 1 elements, but going further is madness.
254    if (!elements.hasNext()) {
255      return of();
256    }
257    E first = elements.next();
258    if (!elements.hasNext()) {
259      return of(first);
260    } else {
261      return new ImmutableList.Builder<E>().add(first).addAll(elements).build();
262    }
263  }
264
265  /**
266   * Returns an immutable list containing the given elements, in order.
267   *
268   * @throws NullPointerException if any of {@code elements} is null
269   * @since 3.0
270   */
271  public static <E> ImmutableList<E> copyOf(E[] elements) {
272    return (elements.length == 0)
273        ? ImmutableList.<E>of()
274        : ImmutableList.<E>construct(elements.clone());
275  }
276
277  /**
278   * Returns an immutable list containing the given elements, sorted according to their natural
279   * order. The sorting algorithm used is stable, so elements that compare as equal will stay in the
280   * order in which they appear in the input.
281   *
282   * <p>If your data has no duplicates, or you wish to deduplicate elements, use {@code
283   * ImmutableSortedSet.copyOf(elements)}; if you want a {@code List} you can use its {@code
284   * asList()} view.
285   *
286   * <p><b>Java 8 users:</b> If you want to convert a {@link java.util.stream.Stream} to a sorted
287   * {@code ImmutableList}, use {@code stream.sorted().collect(toImmutableList())}.
288   *
289   * @throws NullPointerException if any element in the input is null
290   * @since 21.0
291   */
292  public static <E extends Comparable<? super E>> ImmutableList<E> sortedCopyOf(
293      Iterable<? extends E> elements) {
294    Comparable<?>[] array = Iterables.toArray(elements, new Comparable<?>[0]);
295    checkElementsNotNull((Object[]) array);
296    Arrays.sort(array);
297    return asImmutableList(array);
298  }
299
300  /**
301   * Returns an immutable list containing the given elements, in sorted order relative to the
302   * specified comparator. The sorting algorithm used is stable, so elements that compare as equal
303   * will stay in the order in which they appear in the input.
304   *
305   * <p>If your data has no duplicates, or you wish to deduplicate elements, use {@code
306   * ImmutableSortedSet.copyOf(comparator, elements)}; if you want a {@code List} you can use its
307   * {@code asList()} view.
308   *
309   * <p><b>Java 8 users:</b> If you want to convert a {@link java.util.stream.Stream} to a sorted
310   * {@code ImmutableList}, use {@code stream.sorted(comparator).collect(toImmutableList())}.
311   *
312   * @throws NullPointerException if any element in the input is null
313   * @since 21.0
314   */
315  public static <E> ImmutableList<E> sortedCopyOf(
316      Comparator<? super E> comparator, Iterable<? extends E> elements) {
317    checkNotNull(comparator);
318    @SuppressWarnings("unchecked") // all supported methods are covariant
319    E[] array = (E[]) Iterables.toArray(elements);
320    checkElementsNotNull(array);
321    Arrays.sort(array, comparator);
322    return asImmutableList(array);
323  }
324
325  /** Views the array as an immutable list. Checks for nulls; does not copy. */
326  private static <E> ImmutableList<E> construct(Object... elements) {
327    return asImmutableList(checkElementsNotNull(elements));
328  }
329
330  /**
331   * Views the array as an immutable list. Does not check for nulls; does not copy.
332   *
333   * <p>The array must be internally created.
334   */
335  static <E> ImmutableList<E> asImmutableList(Object[] elements) {
336    return asImmutableList(elements, elements.length);
337  }
338
339  /** Views the array as an immutable list. Does not check for nulls. */
340  static <E> ImmutableList<E> asImmutableList(Object[] elements, int length) {
341    if (length == 0) {
342      return of();
343    }
344    return new RegularImmutableList<E>(elements, length);
345  }
346
347  ImmutableList() {}
348
349  // This declaration is needed to make List.iterator() and
350  // ImmutableCollection.iterator() consistent.
351  @Override
352  public UnmodifiableIterator<E> iterator() {
353    return listIterator();
354  }
355
356  @Override
357  public UnmodifiableListIterator<E> listIterator() {
358    return listIterator(0);
359  }
360
361  @SuppressWarnings("unchecked")
362  @Override
363  public UnmodifiableListIterator<E> listIterator(int index) {
364    checkPositionIndex(index, size());
365    if (isEmpty()) {
366      return (UnmodifiableListIterator<E>) EMPTY_ITR;
367    } else {
368      return new Itr<E>(this, index);
369    }
370  }
371
372  /** A singleton implementation of iterator() for the empty ImmutableList. */
373  private static final UnmodifiableListIterator<Object> EMPTY_ITR =
374      new Itr<Object>(RegularImmutableList.EMPTY, 0);
375
376  static class Itr<E> extends AbstractIndexedListIterator<E> {
377    private final ImmutableList<E> list;
378
379    Itr(ImmutableList<E> list, int index) {
380      super(list.size(), index);
381      this.list = list;
382    }
383
384    @Override
385    protected E get(int index) {
386      return list.get(index);
387    }
388  }
389
390  @Override
391  public int indexOf(@NullableDecl Object object) {
392    return (object == null) ? -1 : Lists.indexOfImpl(this, object);
393  }
394
395  @Override
396  public int lastIndexOf(@NullableDecl Object object) {
397    return (object == null) ? -1 : Lists.lastIndexOfImpl(this, object);
398  }
399
400  @Override
401  public boolean contains(@NullableDecl Object object) {
402    return indexOf(object) >= 0;
403  }
404
405  // constrain the return type to ImmutableList<E>
406
407  /**
408   * Returns an immutable list of the elements between the specified {@code fromIndex}, inclusive,
409   * and {@code toIndex}, exclusive. (If {@code fromIndex} and {@code toIndex} are equal, the empty
410   * immutable list is returned.)
411   */
412  @Override
413  public ImmutableList<E> subList(int fromIndex, int toIndex) {
414    checkPositionIndexes(fromIndex, toIndex, size());
415    int length = toIndex - fromIndex;
416    if (length == size()) {
417      return this;
418    } else if (length == 0) {
419      return of();
420    } else {
421      return subListUnchecked(fromIndex, toIndex);
422    }
423  }
424
425  /**
426   * Called by the default implementation of {@link #subList} when {@code toIndex - fromIndex > 1},
427   * after index validation has already been performed.
428   */
429  ImmutableList<E> subListUnchecked(int fromIndex, int toIndex) {
430    return new SubList(fromIndex, toIndex - fromIndex);
431  }
432
433  class SubList extends ImmutableList<E> {
434    final transient int offset;
435    final transient int length;
436
437    SubList(int offset, int length) {
438      this.offset = offset;
439      this.length = length;
440    }
441
442    @Override
443    public int size() {
444      return length;
445    }
446
447    @Override
448    public E get(int index) {
449      checkElementIndex(index, length);
450      return ImmutableList.this.get(index + offset);
451    }
452
453    @Override
454    public ImmutableList<E> subList(int fromIndex, int toIndex) {
455      checkPositionIndexes(fromIndex, toIndex, length);
456      return ImmutableList.this.subList(fromIndex + offset, toIndex + offset);
457    }
458
459    @Override
460    boolean isPartialView() {
461      return true;
462    }
463  }
464
465  /**
466   * Guaranteed to throw an exception and leave the list unmodified.
467   *
468   * @throws UnsupportedOperationException always
469   * @deprecated Unsupported operation.
470   */
471  @CanIgnoreReturnValue
472  @Deprecated
473  @Override
474  public final boolean addAll(int index, Collection<? extends E> newElements) {
475    throw new UnsupportedOperationException();
476  }
477
478  /**
479   * Guaranteed to throw an exception and leave the list unmodified.
480   *
481   * @throws UnsupportedOperationException always
482   * @deprecated Unsupported operation.
483   */
484  @CanIgnoreReturnValue
485  @Deprecated
486  @Override
487  public final E set(int index, E element) {
488    throw new UnsupportedOperationException();
489  }
490
491  /**
492   * Guaranteed to throw an exception and leave the list unmodified.
493   *
494   * @throws UnsupportedOperationException always
495   * @deprecated Unsupported operation.
496   */
497  @Deprecated
498  @Override
499  public final void add(int index, E element) {
500    throw new UnsupportedOperationException();
501  }
502
503  /**
504   * Guaranteed to throw an exception and leave the list unmodified.
505   *
506   * @throws UnsupportedOperationException always
507   * @deprecated Unsupported operation.
508   */
509  @CanIgnoreReturnValue
510  @Deprecated
511  @Override
512  public final E remove(int index) {
513    throw new UnsupportedOperationException();
514  }
515
516  /**
517   * Returns this list instance.
518   *
519   * @since 2.0
520   */
521  @Override
522  public final ImmutableList<E> asList() {
523    return this;
524  }
525
526  @Override
527  int copyIntoArray(Object[] dst, int offset) {
528    // this loop is faster for RandomAccess instances, which ImmutableLists are
529    int size = size();
530    for (int i = 0; i < size; i++) {
531      dst[offset + i] = get(i);
532    }
533    return offset + size;
534  }
535
536  /**
537   * Returns a view of this immutable list in reverse order. For example, {@code ImmutableList.of(1,
538   * 2, 3).reverse()} is equivalent to {@code ImmutableList.of(3, 2, 1)}.
539   *
540   * @return a view of this immutable list in reverse order
541   * @since 7.0
542   */
543  public ImmutableList<E> reverse() {
544    return (size() <= 1) ? this : new ReverseImmutableList<E>(this);
545  }
546
547  private static class ReverseImmutableList<E> extends ImmutableList<E> {
548    private final transient ImmutableList<E> forwardList;
549
550    ReverseImmutableList(ImmutableList<E> backingList) {
551      this.forwardList = backingList;
552    }
553
554    private int reverseIndex(int index) {
555      return (size() - 1) - index;
556    }
557
558    private int reversePosition(int index) {
559      return size() - index;
560    }
561
562    @Override
563    public ImmutableList<E> reverse() {
564      return forwardList;
565    }
566
567    @Override
568    public boolean contains(@NullableDecl Object object) {
569      return forwardList.contains(object);
570    }
571
572    @Override
573    public int indexOf(@NullableDecl Object object) {
574      int index = forwardList.lastIndexOf(object);
575      return (index >= 0) ? reverseIndex(index) : -1;
576    }
577
578    @Override
579    public int lastIndexOf(@NullableDecl Object object) {
580      int index = forwardList.indexOf(object);
581      return (index >= 0) ? reverseIndex(index) : -1;
582    }
583
584    @Override
585    public ImmutableList<E> subList(int fromIndex, int toIndex) {
586      checkPositionIndexes(fromIndex, toIndex, size());
587      return forwardList.subList(reversePosition(toIndex), reversePosition(fromIndex)).reverse();
588    }
589
590    @Override
591    public E get(int index) {
592      checkElementIndex(index, size());
593      return forwardList.get(reverseIndex(index));
594    }
595
596    @Override
597    public int size() {
598      return forwardList.size();
599    }
600
601    @Override
602    boolean isPartialView() {
603      return forwardList.isPartialView();
604    }
605  }
606
607  @Override
608  public boolean equals(@NullableDecl Object obj) {
609    return Lists.equalsImpl(this, obj);
610  }
611
612  @Override
613  public int hashCode() {
614    int hashCode = 1;
615    int n = size();
616    for (int i = 0; i < n; i++) {
617      hashCode = 31 * hashCode + get(i).hashCode();
618
619      hashCode = ~~hashCode;
620      // needed to deal with GWT integer overflow
621    }
622    return hashCode;
623  }
624
625  /*
626   * Serializes ImmutableLists as their logical contents. This ensures that
627   * implementation types do not leak into the serialized representation.
628   */
629  static class SerializedForm implements Serializable {
630    final Object[] elements;
631
632    SerializedForm(Object[] elements) {
633      this.elements = elements;
634    }
635
636    Object readResolve() {
637      return copyOf(elements);
638    }
639
640    private static final long serialVersionUID = 0;
641  }
642
643  private void readObject(ObjectInputStream stream) throws InvalidObjectException {
644    throw new InvalidObjectException("Use SerializedForm");
645  }
646
647  @Override
648  Object writeReplace() {
649    return new SerializedForm(toArray());
650  }
651
652  /**
653   * Returns a new builder. The generated builder is equivalent to the builder created by the {@link
654   * Builder} constructor.
655   */
656  public static <E> Builder<E> builder() {
657    return new Builder<E>();
658  }
659
660  /**
661   * Returns a new builder, expecting the specified number of elements to be added.
662   *
663   * <p>If {@code expectedSize} is exactly the number of elements added to the builder before {@link
664   * Builder#build} is called, the builder is likely to perform better than an unsized {@link
665   * #builder()} would have.
666   *
667   * <p>It is not specified if any performance benefits apply if {@code expectedSize} is close to,
668   * but not exactly, the number of elements added to the builder.
669   *
670   * @since 23.1
671   */
672  @Beta
673  public static <E> Builder<E> builderWithExpectedSize(int expectedSize) {
674    checkNonnegative(expectedSize, "expectedSize");
675    return new ImmutableList.Builder<E>(expectedSize);
676  }
677
678  /**
679   * A builder for creating immutable list instances, especially {@code public static final} lists
680   * ("constant lists"). Example:
681   *
682   * <pre>{@code
683   * public static final ImmutableList<Color> GOOGLE_COLORS
684   *     = new ImmutableList.Builder<Color>()
685   *         .addAll(WEBSAFE_COLORS)
686   *         .add(new Color(0, 191, 255))
687   *         .build();
688   * }</pre>
689   *
690   * <p>Elements appear in the resulting list in the same order they were added to the builder.
691   *
692   * <p>Builder instances can be reused; it is safe to call {@link #build} multiple times to build
693   * multiple lists in series. Each new list contains all the elements of the ones created before
694   * it.
695   *
696   * @since 2.0
697   */
698  public static final class Builder<E> extends ImmutableCollection.ArrayBasedBuilder<E> {
699    /**
700     * Creates a new builder. The returned builder is equivalent to the builder generated by {@link
701     * ImmutableList#builder}.
702     */
703    public Builder() {
704      this(DEFAULT_INITIAL_CAPACITY);
705    }
706
707    Builder(int capacity) {
708      super(capacity);
709    }
710
711    /**
712     * Adds {@code element} to the {@code ImmutableList}.
713     *
714     * @param element the element to add
715     * @return this {@code Builder} object
716     * @throws NullPointerException if {@code element} is null
717     */
718    @CanIgnoreReturnValue
719    @Override
720    public Builder<E> add(E element) {
721      super.add(element);
722      return this;
723    }
724
725    /**
726     * Adds each element of {@code elements} to the {@code ImmutableList}.
727     *
728     * @param elements the {@code Iterable} to add to the {@code ImmutableList}
729     * @return this {@code Builder} object
730     * @throws NullPointerException if {@code elements} is null or contains a null element
731     */
732    @CanIgnoreReturnValue
733    @Override
734    public Builder<E> add(E... elements) {
735      super.add(elements);
736      return this;
737    }
738
739    /**
740     * Adds each element of {@code elements} to the {@code ImmutableList}.
741     *
742     * @param elements the {@code Iterable} to add to the {@code ImmutableList}
743     * @return this {@code Builder} object
744     * @throws NullPointerException if {@code elements} is null or contains a null element
745     */
746    @CanIgnoreReturnValue
747    @Override
748    public Builder<E> addAll(Iterable<? extends E> elements) {
749      super.addAll(elements);
750      return this;
751    }
752
753    /**
754     * Adds each element of {@code elements} to the {@code ImmutableList}.
755     *
756     * @param elements the {@code Iterable} to add to the {@code ImmutableList}
757     * @return this {@code Builder} object
758     * @throws NullPointerException if {@code elements} is null or contains a null element
759     */
760    @CanIgnoreReturnValue
761    @Override
762    public Builder<E> addAll(Iterator<? extends E> elements) {
763      super.addAll(elements);
764      return this;
765    }
766
767    /**
768     * Returns a newly-created {@code ImmutableList} based on the contents of the {@code Builder}.
769     */
770    @Override
771    public ImmutableList<E> build() {
772      forceCopy = true;
773      return asImmutableList(contents, size);
774    }
775  }
776}