Source code

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#singletonList}, 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, "the total number of elements must fit in an int");
189    Object[] array = new Object[12 + others.length];
190    array[0] = e1;
191    array[1] = e2;
192    array[2] = e3;
193    array[3] = e4;
194    array[4] = e5;
195    array[5] = e6;
196    array[6] = e7;
197    array[7] = e8;
198    array[8] = e9;
199    array[9] = e10;
200    array[10] = e11;
201    array[11] = e12;
202    System.arraycopy(others, 0, array, 12, others.length);
203    return construct(array);
204  }
205
206  /**
207   * Returns an immutable list containing the given elements, in order. If {@code elements} is a
208   * {@link Collection}, this method behaves exactly as {@link #copyOf(Collection)}; otherwise, it
209   * behaves exactly as {@code copyOf(elements.iterator()}.
210   *
211   * @throws NullPointerException if {@code elements} contains a null element
212   */
213  public static <E> ImmutableList<E> copyOf(Iterable<? extends E> elements) {
214    checkNotNull(elements); // TODO(kevinb): is this here only for GWT?
215    return (elements instanceof Collection)
216        ? copyOf((Collection<? extends E>) elements)
217        : copyOf(elements.iterator());
218  }
219
220  /**
221   * Returns an immutable list containing the given elements, in order.
222   *
223   * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
224   * safe to do so. The exact circumstances under which a copy will or will not be performed are
225   * undocumented and subject to change.
226   *
227   * <p>Note that if {@code list} is a {@code List<String>}, then {@code ImmutableList.copyOf(list)}
228   * returns an {@code ImmutableList<String>} containing each of the strings in {@code list}, while
229   * ImmutableList.of(list)} returns an {@code ImmutableList<List<String>>} containing one element
230   * (the given list itself).
231   *
232   * <p>This method is safe to use even when {@code elements} is a synchronized or concurrent
233   * collection that is currently being modified by another thread.
234   *
235   * @throws NullPointerException if {@code elements} contains a null element
236   */
237  public static <E> ImmutableList<E> copyOf(Collection<? extends E> elements) {
238    if (elements instanceof ImmutableCollection) {
239      @SuppressWarnings("unchecked") // all supported methods are covariant
240      ImmutableList<E> list = ((ImmutableCollection<E>) elements).asList();
241      return list.isPartialView() ? ImmutableList.<E>asImmutableList(list.toArray()) : list;
242    }
243    return construct(elements.toArray());
244  }
245
246  /**
247   * Returns an immutable list containing the given elements, in order.
248   *
249   * @throws NullPointerException if {@code elements} contains a null element
250   */
251  public static <E> ImmutableList<E> copyOf(Iterator<? extends E> elements) {
252    // We special-case for 0 or 1 elements, but going further is madness.
253    if (!elements.hasNext()) {
254      return of();
255    }
256    E first = elements.next();
257    if (!elements.hasNext()) {
258      return of(first);
259    } else {
260      return new ImmutableList.Builder<E>().add(first).addAll(elements).build();
261    }
262  }
263
264  /**
265   * Returns an immutable list containing the given elements, in order.
266   *
267   * @throws NullPointerException if {@code elements} contains a null element
268   * @since 3.0
269   */
270  public static <E> ImmutableList<E> copyOf(E[] elements) {
271    return (elements.length == 0)
272        ? ImmutableList.<E>of()
273        : ImmutableList.<E>construct(elements.clone());
274  }
275
276  /**
277   * Returns an immutable list containing the given elements, sorted according to their natural
278   * order. The sorting algorithm used is stable, so elements that compare as equal will stay in the
279   * order in which they appear in the input.
280   *
281   * <p>If your data has no duplicates, or you wish to deduplicate elements, use {@code
282   * ImmutableSortedSet.copyOf(elements)}; if you want a {@code List} you can use its {@code
283   * asList()} view.
284   *
285   * <p><b>Java 8 users:</b> If you want to convert a {@link java.util.stream.Stream} to a sorted
286   * {@code ImmutableList}, use {@code stream.sorted().collect(toImmutableList())}.
287   *
288   * @throws NullPointerException if any element in the input is null
289   * @since 21.0
290   */
291  public static <E extends Comparable<? super E>> ImmutableList<E> sortedCopyOf(
292      Iterable<? extends E> elements) {
293    Comparable<?>[] array = Iterables.toArray(elements, new Comparable<?>[0]);
294    checkElementsNotNull((Object[]) array);
295    Arrays.sort(array);
296    return asImmutableList(array);
297  }
298
299  /**
300   * Returns an immutable list containing the given elements, in sorted order relative to the
301   * specified comparator. The sorting algorithm used is stable, so elements that compare as equal
302   * will stay in the order in which they appear in the input.
303   *
304   * <p>If your data has no duplicates, or you wish to deduplicate elements, use {@code
305   * ImmutableSortedSet.copyOf(comparator, elements)}; if you want a {@code List} you can use its
306   * {@code asList()} view.
307   *
308   * <p><b>Java 8 users:</b> If you want to convert a {@link java.util.stream.Stream} to a sorted
309   * {@code ImmutableList}, use {@code stream.sorted(comparator).collect(toImmutableList())}.
310   *
311   * @throws NullPointerException if any element in the input is null
312   * @since 21.0
313   */
314  public static <E> ImmutableList<E> sortedCopyOf(
315      Comparator<? super E> comparator, Iterable<? extends E> elements) {
316    checkNotNull(comparator);
317    @SuppressWarnings("unchecked") // all supported methods are covariant
318    E[] array = (E[]) Iterables.toArray(elements);
319    checkElementsNotNull(array);
320    Arrays.sort(array, comparator);
321    return asImmutableList(array);
322  }
323
324  /** Views the array as an immutable list. Checks for nulls; does not copy. */
325  private static <E> ImmutableList<E> construct(Object... elements) {
326    return asImmutableList(checkElementsNotNull(elements));
327  }
328
329  /**
330   * Views the array as an immutable list. Does not check for nulls; does not copy.
331   *
332   * <p>The array must be internally created.
333   */
334  static <E> ImmutableList<E> asImmutableList(Object[] elements) {
335    return asImmutableList(elements, elements.length);
336  }
337
338  /** Views the array as an immutable list. Does not check for nulls. */
339  static <E> ImmutableList<E> asImmutableList(Object[] elements, int length) {
340    if (length == 0) {
341      return of();
342    }
343    return new RegularImmutableList<E>(elements, length);
344  }
345
346  ImmutableList() {}
347
348  // This declaration is needed to make List.iterator() and
349  // ImmutableCollection.iterator() consistent.
350  @Override
351  public UnmodifiableIterator<E> iterator() {
352    return listIterator();
353  }
354
355  @Override
356  public UnmodifiableListIterator<E> listIterator() {
357    return listIterator(0);
358  }
359
360  @SuppressWarnings("unchecked")
361  @Override
362  public UnmodifiableListIterator<E> listIterator(int index) {
363    checkPositionIndex(index, size());
364    if (isEmpty()) {
365      return (UnmodifiableListIterator<E>) EMPTY_ITR;
366    } else {
367      return new Itr<E>(this, index);
368    }
369  }
370
371  /** A singleton implementation of iterator() for the empty ImmutableList. */
372  private static final UnmodifiableListIterator<Object> EMPTY_ITR =
373      new Itr<Object>(RegularImmutableList.EMPTY, 0);
374
375  static class Itr<E> extends AbstractIndexedListIterator<E> {
376    private final ImmutableList<E> list;
377
378    Itr(ImmutableList<E> list, int index) {
379      super(list.size(), index);
380      this.list = list;
381    }
382
383    @Override
384    protected E get(int index) {
385      return list.get(index);
386    }
387  }
388
389  @Override
390  public int indexOf(@NullableDecl Object object) {
391    return (object == null) ? -1 : Lists.indexOfImpl(this, object);
392  }
393
394  @Override
395  public int lastIndexOf(@NullableDecl Object object) {
396    return (object == null) ? -1 : Lists.lastIndexOfImpl(this, object);
397  }
398
399  @Override
400  public boolean contains(@NullableDecl Object object) {
401    return indexOf(object) >= 0;
402  }
403
404  // constrain the return type to ImmutableList<E>
405
406  /**
407   * Returns an immutable list of the elements between the specified {@code fromIndex}, inclusive,
408   * and {@code toIndex}, exclusive. (If {@code fromIndex} and {@code toIndex} are equal, the empty
409   * immutable list is returned.)
410   */
411  @Override
412  public ImmutableList<E> subList(int fromIndex, int toIndex) {
413    checkPositionIndexes(fromIndex, toIndex, size());
414    int length = toIndex - fromIndex;
415    if (length == size()) {
416      return this;
417    } else if (length == 0) {
418      return of();
419    } else {
420      return subListUnchecked(fromIndex, toIndex);
421    }
422  }
423
424  /**
425   * Called by the default implementation of {@link #subList} when {@code toIndex - fromIndex > 1},
426   * after index validation has already been performed.
427   */
428  ImmutableList<E> subListUnchecked(int fromIndex, int toIndex) {
429    return new SubList(fromIndex, toIndex - fromIndex);
430  }
431
432  class SubList extends ImmutableList<E> {
433    final transient int offset;
434    final transient int length;
435
436    SubList(int offset, int length) {
437      this.offset = offset;
438      this.length = length;
439    }
440
441    @Override
442    public int size() {
443      return length;
444    }
445
446    @Override
447    Object[] internalArray() {
448      return ImmutableList.this.internalArray();
449    }
450
451    @Override
452    int internalArrayStart() {
453      return ImmutableList.this.internalArrayStart() + offset;
454    }
455
456    @Override
457    int internalArrayEnd() {
458      return ImmutableList.this.internalArrayStart() + offset + length;
459    }
460
461    @Override
462    public E get(int index) {
463      checkElementIndex(index, length);
464      return ImmutableList.this.get(index + offset);
465    }
466
467    @Override
468    public ImmutableList<E> subList(int fromIndex, int toIndex) {
469      checkPositionIndexes(fromIndex, toIndex, length);
470      return ImmutableList.this.subList(fromIndex + offset, toIndex + offset);
471    }
472
473    @Override
474    boolean isPartialView() {
475      return true;
476    }
477  }
478
479  /**
480   * Guaranteed to throw an exception and leave the list unmodified.
481   *
482   * @throws UnsupportedOperationException always
483   * @deprecated Unsupported operation.
484   */
485  @CanIgnoreReturnValue
486  @Deprecated
487  @Override
488  public final boolean addAll(int index, Collection<? extends E> newElements) {
489    throw new UnsupportedOperationException();
490  }
491
492  /**
493   * Guaranteed to throw an exception and leave the list unmodified.
494   *
495   * @throws UnsupportedOperationException always
496   * @deprecated Unsupported operation.
497   */
498  @CanIgnoreReturnValue
499  @Deprecated
500  @Override
501  public final E set(int index, E element) {
502    throw new UnsupportedOperationException();
503  }
504
505  /**
506   * Guaranteed to throw an exception and leave the list unmodified.
507   *
508   * @throws UnsupportedOperationException always
509   * @deprecated Unsupported operation.
510   */
511  @Deprecated
512  @Override
513  public final void add(int index, E element) {
514    throw new UnsupportedOperationException();
515  }
516
517  /**
518   * Guaranteed to throw an exception and leave the list unmodified.
519   *
520   * @throws UnsupportedOperationException always
521   * @deprecated Unsupported operation.
522   */
523  @CanIgnoreReturnValue
524  @Deprecated
525  @Override
526  public final E remove(int index) {
527    throw new UnsupportedOperationException();
528  }
529
530  /**
531   * Returns this list instance.
532   *
533   * @since 2.0
534   */
535  @Override
536  public final ImmutableList<E> asList() {
537    return this;
538  }
539
540  @Override
541  int copyIntoArray(Object[] dst, int offset) {
542    // this loop is faster for RandomAccess instances, which ImmutableLists are
543    int size = size();
544    for (int i = 0; i < size; i++) {
545      dst[offset + i] = get(i);
546    }
547    return offset + size;
548  }
549
550  /**
551   * Returns a view of this immutable list in reverse order. For example, {@code ImmutableList.of(1,
552   * 2, 3).reverse()} is equivalent to {@code ImmutableList.of(3, 2, 1)}.
553   *
554   * @return a view of this immutable list in reverse order
555   * @since 7.0
556   */
557  public ImmutableList<E> reverse() {
558    return (size() <= 1) ? this : new ReverseImmutableList<E>(this);
559  }
560
561  private static class ReverseImmutableList<E> extends ImmutableList<E> {
562    private final transient ImmutableList<E> forwardList;
563
564    ReverseImmutableList(ImmutableList<E> backingList) {
565      this.forwardList = backingList;
566    }
567
568    private int reverseIndex(int index) {
569      return (size() - 1) - index;
570    }
571
572    private int reversePosition(int index) {
573      return size() - index;
574    }
575
576    @Override
577    public ImmutableList<E> reverse() {
578      return forwardList;
579    }
580
581    @Override
582    public boolean contains(@NullableDecl Object object) {
583      return forwardList.contains(object);
584    }
585
586    @Override
587    public int indexOf(@NullableDecl Object object) {
588      int index = forwardList.lastIndexOf(object);
589      return (index >= 0) ? reverseIndex(index) : -1;
590    }
591
592    @Override
593    public int lastIndexOf(@NullableDecl Object object) {
594      int index = forwardList.indexOf(object);
595      return (index >= 0) ? reverseIndex(index) : -1;
596    }
597
598    @Override
599    public ImmutableList<E> subList(int fromIndex, int toIndex) {
600      checkPositionIndexes(fromIndex, toIndex, size());
601      return forwardList.subList(reversePosition(toIndex), reversePosition(fromIndex)).reverse();
602    }
603
604    @Override
605    public E get(int index) {
606      checkElementIndex(index, size());
607      return forwardList.get(reverseIndex(index));
608    }
609
610    @Override
611    public int size() {
612      return forwardList.size();
613    }
614
615    @Override
616    boolean isPartialView() {
617      return forwardList.isPartialView();
618    }
619  }
620
621  @Override
622  public boolean equals(@NullableDecl Object obj) {
623    return Lists.equalsImpl(this, obj);
624  }
625
626  @Override
627  public int hashCode() {
628    int hashCode = 1;
629    int n = size();
630    for (int i = 0; i < n; i++) {
631      hashCode = 31 * hashCode + get(i).hashCode();
632
633      hashCode = ~~hashCode;
634      // needed to deal with GWT integer overflow
635    }
636    return hashCode;
637  }
638
639  /*
640   * Serializes ImmutableLists as their logical contents. This ensures that
641   * implementation types do not leak into the serialized representation.
642   */
643  static class SerializedForm implements Serializable {
644    final Object[] elements;
645
646    SerializedForm(Object[] elements) {
647      this.elements = elements;
648    }
649
650    Object readResolve() {
651      return copyOf(elements);
652    }
653
654    private static final long serialVersionUID = 0;
655  }
656
657  private void readObject(ObjectInputStream stream) throws InvalidObjectException {
658    throw new InvalidObjectException("Use SerializedForm");
659  }
660
661  @Override
662  Object writeReplace() {
663    return new SerializedForm(toArray());
664  }
665
666  /**
667   * Returns a new builder. The generated builder is equivalent to the builder created by the {@link
668   * Builder} constructor.
669   */
670  public static <E> Builder<E> builder() {
671    return new Builder<E>();
672  }
673
674  /**
675   * Returns a new builder, expecting the specified number of elements to be added.
676   *
677   * <p>If {@code expectedSize} is exactly the number of elements added to the builder before {@link
678   * Builder#build} is called, the builder is likely to perform better than an unsized {@link
679   * #builder()} would have.
680   *
681   * <p>It is not specified if any performance benefits apply if {@code expectedSize} is close to,
682   * but not exactly, the number of elements added to the builder.
683   *
684   * @since 23.1
685   */
686  @Beta
687  public static <E> Builder<E> builderWithExpectedSize(int expectedSize) {
688    checkNonnegative(expectedSize, "expectedSize");
689    return new ImmutableList.Builder<E>(expectedSize);
690  }
691
692  /**
693   * A builder for creating immutable list instances, especially {@code public static final} lists
694   * ("constant lists"). Example:
695   *
696   * <pre>{@code
697   * public static final ImmutableList<Color> GOOGLE_COLORS
698   *     = new ImmutableList.Builder<Color>()
699   *         .addAll(WEBSAFE_COLORS)
700   *         .add(new Color(0, 191, 255))
701   *         .build();
702   * }</pre>
703   *
704   * <p>Elements appear in the resulting list in the same order they were added to the builder.
705   *
706   * <p>Builder instances can be reused; it is safe to call {@link #build} multiple times to build
707   * multiple lists in series. Each new list contains all the elements of the ones created before
708   * it.
709   *
710   * @since 2.0
711   */
712  public static final class Builder<E> extends ImmutableCollection.ArrayBasedBuilder<E> {
713    /**
714     * Creates a new builder. The returned builder is equivalent to the builder generated by {@link
715     * ImmutableList#builder}.
716     */
717    public Builder() {
718      this(DEFAULT_INITIAL_CAPACITY);
719    }
720
721    Builder(int capacity) {
722      super(capacity);
723    }
724
725    /**
726     * Adds {@code element} to the {@code ImmutableList}.
727     *
728     * @param element the element to add
729     * @return this {@code Builder} object
730     * @throws NullPointerException if {@code element} is null
731     */
732    @CanIgnoreReturnValue
733    @Override
734    public Builder<E> add(E element) {
735      super.add(element);
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> add(E... elements) {
749      super.add(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(Iterable<? extends E> elements) {
763      super.addAll(elements);
764      return this;
765    }
766
767    /**
768     * Adds each element of {@code elements} to the {@code ImmutableList}.
769     *
770     * @param elements the {@code Iterator} to add to the {@code ImmutableList}
771     * @return this {@code Builder} object
772     * @throws NullPointerException if {@code elements} is null or contains a null element
773     */
774    @CanIgnoreReturnValue
775    @Override
776    public Builder<E> addAll(Iterator<? extends E> elements) {
777      super.addAll(elements);
778      return this;
779    }
780
781    @CanIgnoreReturnValue
782    Builder<E> combine(Builder<E> other) {
783      addAll(other.contents, other.size);
784      return this;
785    }
786
787    /**
788     * Returns a newly-created {@code ImmutableList} based on the contents of the {@code Builder}.
789     */
790    @Override
791    public ImmutableList<E> build() {
792      forceCopy = true;
793      return asImmutableList(contents, size);
794    }
795  }
796}