374 lines
10 KiB
Java
374 lines
10 KiB
Java
/*
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* Copyright (C) 2008 The Guava Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.common.collect;
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import static com.google.common.base.Preconditions.checkNotNull;
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import static com.google.common.collect.CollectPreconditions.checkNonnegative;
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import static com.google.common.collect.ObjectArrays.checkElementsNotNull;
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import java.io.Serializable;
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import java.util.AbstractCollection;
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import java.util.Collection;
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import java.util.Iterator;
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import javax.annotation.Nullable;
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import com.google.common.annotations.GwtCompatible;
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/**
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* An immutable collection. Does not permit null elements.
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*
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* <p>
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* In addition to the {@link Collection} methods, this class has an
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* {@link #asList()} method, which returns a list view of the collection's
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* elements.
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*
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* <p>
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* <b>Note:</b> Although this class is not final, it cannot be subclassed
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* outside of this package as it has no public or protected constructors. Thus,
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* instances of this type are guaranteed to be immutable.
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*
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* @author Jesse Wilson
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* @since 2.0 (imported from Google Collections Library)
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*/
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@GwtCompatible(emulated = true)
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@SuppressWarnings("serial") // we're overriding default serialization
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public abstract class ImmutableCollection<E> extends AbstractCollection<E> implements Serializable {
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ImmutableCollection() {
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}
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/**
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* Returns an unmodifiable iterator across the elements in this collection.
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*/
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@Override
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public abstract UnmodifiableIterator<E> iterator();
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@Override
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public final Object[] toArray() {
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int size = size();
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if (size == 0) {
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return ObjectArrays.EMPTY_ARRAY;
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}
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Object[] result = new Object[size()];
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copyIntoArray(result, 0);
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return result;
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}
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@Override
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public final <T> T[] toArray(T[] other) {
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checkNotNull(other);
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int size = size();
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if (other.length < size) {
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other = ObjectArrays.newArray(other, size);
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} else if (other.length > size) {
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other[size] = null;
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}
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copyIntoArray(other, 0);
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return other;
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}
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@Override
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public boolean contains(@Nullable Object object) {
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return object != null && super.contains(object);
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}
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/**
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* Guaranteed to throw an exception and leave the collection unmodified.
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*
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* @throws UnsupportedOperationException always
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* @deprecated Unsupported operation.
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*/
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@Deprecated
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@Override
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public final boolean add(E e) {
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throw new UnsupportedOperationException();
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}
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/**
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* Guaranteed to throw an exception and leave the collection unmodified.
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*
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* @throws UnsupportedOperationException always
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* @deprecated Unsupported operation.
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*/
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@Deprecated
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@Override
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public final boolean remove(Object object) {
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throw new UnsupportedOperationException();
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}
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/**
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* Guaranteed to throw an exception and leave the collection unmodified.
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*
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* @throws UnsupportedOperationException always
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* @deprecated Unsupported operation.
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*/
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@Deprecated
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@Override
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public final boolean addAll(Collection<? extends E> newElements) {
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throw new UnsupportedOperationException();
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}
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/**
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* Guaranteed to throw an exception and leave the collection unmodified.
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*
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* @throws UnsupportedOperationException always
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* @deprecated Unsupported operation.
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*/
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@Deprecated
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@Override
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public final boolean removeAll(Collection<?> oldElements) {
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throw new UnsupportedOperationException();
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}
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/**
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* Guaranteed to throw an exception and leave the collection unmodified.
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*
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* @throws UnsupportedOperationException always
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* @deprecated Unsupported operation.
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*/
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@Deprecated
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@Override
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public final boolean retainAll(Collection<?> elementsToKeep) {
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throw new UnsupportedOperationException();
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}
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/**
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* Guaranteed to throw an exception and leave the collection unmodified.
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*
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* @throws UnsupportedOperationException always
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* @deprecated Unsupported operation.
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*/
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@Deprecated
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@Override
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public final void clear() {
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throw new UnsupportedOperationException();
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}
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/*
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* TODO(kevinb): Restructure code so ImmutableList doesn't contain this
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* variable, which it doesn't use.
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*/
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private transient ImmutableList<E> asList;
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/**
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* Returns a list view of the collection.
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*
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* @since 2.0
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*/
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public ImmutableList<E> asList() {
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ImmutableList<E> list = asList;
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return (list == null) ? (asList = createAsList()) : list;
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}
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ImmutableList<E> createAsList() {
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switch (size()) {
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case 0:
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return ImmutableList.of();
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case 1:
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return ImmutableList.of(iterator().next());
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default:
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return new RegularImmutableAsList<E>(this, toArray());
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}
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}
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/**
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* Returns {@code true} if this immutable collection's implementation contains
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* references to user-created objects that aren't accessible via this
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* collection's methods. This is generally used to determine whether
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* {@code copyOf} implementations should make an explicit copy to avoid memory
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* leaks.
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*/
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abstract boolean isPartialView();
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/**
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* Copies the contents of this immutable collection into the specified array at
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* the specified offset. Returns {@code offset + size()}.
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*/
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int copyIntoArray(Object[] dst, int offset) {
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for (E e : this) {
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dst[offset++] = e;
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}
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return offset;
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}
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Object writeReplace() {
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// We serialize by default to ImmutableList, the simplest thing that works.
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return new ImmutableList.SerializedForm(toArray());
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}
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/**
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* Abstract base class for builders of {@link ImmutableCollection} types.
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*
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* @since 10.0
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*/
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public abstract static class Builder<E> {
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static final int DEFAULT_INITIAL_CAPACITY = 4;
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static int expandedCapacity(int oldCapacity, int minCapacity) {
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if (minCapacity < 0) {
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throw new AssertionError("cannot store more than MAX_VALUE elements");
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}
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// careful of overflow!
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int newCapacity = oldCapacity + (oldCapacity >> 1) + 1;
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if (newCapacity < minCapacity) {
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newCapacity = Integer.highestOneBit(minCapacity - 1) << 1;
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}
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if (newCapacity < 0) {
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newCapacity = Integer.MAX_VALUE;
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// guaranteed to be >= newCapacity
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}
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return newCapacity;
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}
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Builder() {
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}
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/**
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* Adds {@code element} to the {@code ImmutableCollection} being built.
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*
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* <p>
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* Note that each builder class covariantly returns its own type from this
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* method.
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*
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* @param element the element to add
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* @return this {@code Builder} instance
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* @throws NullPointerException if {@code element} is null
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*/
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public abstract Builder<E> add(E element);
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/**
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* Adds each element of {@code elements} to the {@code ImmutableCollection}
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* being built.
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*
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* <p>
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* Note that each builder class overrides this method in order to covariantly
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* return its own type.
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*
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* @param elements the elements to add
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* @return this {@code Builder} instance
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* @throws NullPointerException if {@code elements} is null or contains a null
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* element
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*/
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public Builder<E> add(E... elements) {
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for (E element : elements) {
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add(element);
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}
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return this;
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}
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/**
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* Adds each element of {@code elements} to the {@code ImmutableCollection}
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* being built.
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*
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* <p>
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* Note that each builder class overrides this method in order to covariantly
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* return its own type.
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*
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* @param elements the elements to add
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* @return this {@code Builder} instance
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* @throws NullPointerException if {@code elements} is null or contains a null
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* element
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*/
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public Builder<E> addAll(Iterable<? extends E> elements) {
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for (E element : elements) {
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add(element);
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}
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return this;
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}
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/**
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* Adds each element of {@code elements} to the {@code ImmutableCollection}
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* being built.
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*
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* <p>
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* Note that each builder class overrides this method in order to covariantly
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* return its own type.
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*
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* @param elements the elements to add
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* @return this {@code Builder} instance
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* @throws NullPointerException if {@code elements} is null or contains a null
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* element
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*/
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public Builder<E> addAll(Iterator<? extends E> elements) {
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while (elements.hasNext()) {
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add(elements.next());
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}
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return this;
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}
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/**
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* Returns a newly-created {@code ImmutableCollection} of the appropriate type,
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* containing the elements provided to this builder.
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*
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* <p>
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* Note that each builder class covariantly returns the appropriate type of
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* {@code ImmutableCollection} from this method.
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*/
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public abstract ImmutableCollection<E> build();
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}
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abstract static class ArrayBasedBuilder<E> extends ImmutableCollection.Builder<E> {
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Object[] contents;
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int size;
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ArrayBasedBuilder(int initialCapacity) {
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checkNonnegative(initialCapacity, "initialCapacity");
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this.contents = new Object[initialCapacity];
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this.size = 0;
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}
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/**
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* Expand the absolute capacity of the builder so it can accept at least the
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* specified number of elements without being resized.
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*/
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private void ensureCapacity(int minCapacity) {
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if (contents.length < minCapacity) {
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this.contents = ObjectArrays.arraysCopyOf(this.contents,
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expandedCapacity(contents.length, minCapacity));
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}
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}
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@Override
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public ArrayBasedBuilder<E> add(E element) {
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checkNotNull(element);
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ensureCapacity(size + 1);
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contents[size++] = element;
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return this;
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}
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@Override
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public Builder<E> add(E... elements) {
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checkElementsNotNull(elements);
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ensureCapacity(size + elements.length);
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System.arraycopy(elements, 0, contents, size, elements.length);
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size += elements.length;
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return this;
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}
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@Override
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public Builder<E> addAll(Iterable<? extends E> elements) {
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if (elements instanceof Collection) {
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Collection<?> collection = (Collection<?>) elements;
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ensureCapacity(size + collection.size());
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}
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super.addAll(elements);
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return this;
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}
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}
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}
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