282 lines
8.8 KiB
Java
282 lines
8.8 KiB
Java
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/*
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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 java.util.Map;
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import com.google.common.annotations.GwtCompatible;
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/**
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* An immutable {@link BiMap} with reliable user-specified iteration order. Does
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* not permit null keys or values. An {@code ImmutableBiMap} and its inverse
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* have the same iteration ordering.
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*
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* <p>
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* An instance of {@code ImmutableBiMap} contains its own data and will
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* <i>never</i> change. {@code ImmutableBiMap} is convenient for
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* {@code public static final} maps ("constant maps") and also lets you easily
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* make a "defensive copy" of a bimap provided to your class by a caller.
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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 as it
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* has no public or protected constructors. Thus, instances of this class are
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* guaranteed to be immutable.
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*
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* @author Jared Levy
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* @since 2.0 (imported from Google Collections Library)
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*/
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@GwtCompatible(serializable = true, emulated = true)
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public abstract class ImmutableBiMap<K, V> extends ImmutableMap<K, V> implements BiMap<K, V> {
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/**
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* Returns the empty bimap.
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*/
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// Casting to any type is safe because the set will never hold any elements.
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@SuppressWarnings("unchecked")
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public static <K, V> ImmutableBiMap<K, V> of() {
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return (ImmutableBiMap<K, V>) EmptyImmutableBiMap.INSTANCE;
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}
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/**
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* Returns an immutable bimap containing a single entry.
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*/
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public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1) {
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return new SingletonImmutableBiMap<K, V>(k1, v1);
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}
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/**
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* Returns an immutable map containing the given entries, in order.
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*
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* @throws IllegalArgumentException if duplicate keys or values are added
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*/
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public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2) {
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return new RegularImmutableBiMap<K, V>(entryOf(k1, v1), entryOf(k2, v2));
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}
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/**
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* Returns an immutable map containing the given entries, in order.
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*
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* @throws IllegalArgumentException if duplicate keys or values are added
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*/
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public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3) {
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return new RegularImmutableBiMap<K, V>(entryOf(k1, v1), entryOf(k2, v2), entryOf(k3, v3));
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}
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/**
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* Returns an immutable map containing the given entries, in order.
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*
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* @throws IllegalArgumentException if duplicate keys or values are added
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*/
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public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
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return new RegularImmutableBiMap<K, V>(entryOf(k1, v1), entryOf(k2, v2), entryOf(k3, v3), entryOf(k4, v4));
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}
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/**
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* Returns an immutable map containing the given entries, in order.
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*
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* @throws IllegalArgumentException if duplicate keys or values are added
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*/
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public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
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return new RegularImmutableBiMap<K, V>(entryOf(k1, v1), entryOf(k2, v2), entryOf(k3, v3), entryOf(k4, v4),
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entryOf(k5, v5));
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}
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// looking for of() with > 5 entries? Use the builder instead.
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/**
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* Returns a new builder. The generated builder is equivalent to the builder
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* created by the {@link Builder} constructor.
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*/
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public static <K, V> Builder<K, V> builder() {
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return new Builder<K, V>();
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}
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/**
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* A builder for creating immutable bimap instances, especially {@code public
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* static final} bimaps ("constant bimaps"). Example:
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*
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* <pre>
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* {
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* @code
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*
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* static final ImmutableBiMap<String, Integer> WORD_TO_INT = new ImmutableBiMap.Builder<String, Integer>()
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* .put("one", 1).put("two", 2).put("three", 3).build();
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* }
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* </pre>
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*
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* <p>
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* For <i>small</i> immutable bimaps, the {@code ImmutableBiMap.of()} methods
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* are even more convenient.
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*
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* <p>
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* Builder instances can be reused - it is safe to call {@link #build} multiple
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* times to build multiple bimaps in series. Each bimap is a superset of the
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* bimaps created before it.
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*
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* @since 2.0 (imported from Google Collections Library)
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*/
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public static final class Builder<K, V> extends ImmutableMap.Builder<K, V> {
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/**
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* Creates a new builder. The returned builder is equivalent to the builder
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* generated by {@link ImmutableBiMap#builder}.
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*/
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public Builder() {
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}
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/**
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* Associates {@code key} with {@code value} in the built bimap. Duplicate keys
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* or values are not allowed, and will cause {@link #build} to fail.
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*/
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@Override
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public Builder<K, V> put(K key, V value) {
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super.put(key, value);
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return this;
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}
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/**
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* Associates all of the given map's keys and values in the built bimap.
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* Duplicate keys or values are not allowed, and will cause {@link #build} to
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* fail.
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*
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* @throws NullPointerException if any key or value in {@code map} is null
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*/
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@Override
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public Builder<K, V> putAll(Map<? extends K, ? extends V> map) {
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super.putAll(map);
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return this;
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}
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/**
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* Returns a newly-created immutable bimap.
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*
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* @throws IllegalArgumentException if duplicate keys or values were added
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*/
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@Override
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public ImmutableBiMap<K, V> build() {
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switch (size) {
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case 0:
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return of();
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case 1:
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return of(entries[0].getKey(), entries[0].getValue());
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default:
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return new RegularImmutableBiMap<K, V>(size, entries);
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}
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}
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}
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/**
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* Returns an immutable bimap containing the same entries as {@code map}. If
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* {@code map} somehow contains entries with duplicate keys (for example, if it
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* is a {@code SortedMap} whose comparator is not <i>consistent with
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* equals</i>), the results of this method are undefined.
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*
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* <p>
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* Despite the method name, this method attempts to avoid actually copying the
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* data when it is safe to do so. The exact circumstances under which a copy
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* will or will not be performed are undocumented and subject to change.
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*
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* @throws IllegalArgumentException if two keys have the same value
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* @throws NullPointerException if any key or value in {@code map} is null
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*/
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public static <K, V> ImmutableBiMap<K, V> copyOf(Map<? extends K, ? extends V> map) {
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if (map instanceof ImmutableBiMap) {
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@SuppressWarnings("unchecked") // safe since map is not writable
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ImmutableBiMap<K, V> bimap = (ImmutableBiMap<K, V>) map;
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// TODO(user): if we need to make a copy of a BiMap because the
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// forward map is a view, don't make a copy of the non-view delegate map
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if (!bimap.isPartialView()) {
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return bimap;
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}
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}
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Entry<?, ?>[] entries = map.entrySet().toArray(EMPTY_ENTRY_ARRAY);
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switch (entries.length) {
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case 0:
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return of();
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case 1:
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@SuppressWarnings("unchecked") // safe covariant cast in this context
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Entry<K, V> entry = (Entry<K, V>) entries[0];
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return of(entry.getKey(), entry.getValue());
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default:
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return new RegularImmutableBiMap<K, V>(entries);
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}
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}
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private static final Entry<?, ?>[] EMPTY_ENTRY_ARRAY = new Entry<?, ?>[0];
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ImmutableBiMap() {
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}
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/**
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* {@inheritDoc}
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*
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* <p>
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* The inverse of an {@code ImmutableBiMap} is another {@code ImmutableBiMap}.
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*/
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@Override
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public abstract ImmutableBiMap<V, K> inverse();
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/**
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* Returns an immutable set of the values in this map. The values are in the
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* same order as the parameters used to build this map.
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*/
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@Override
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public ImmutableSet<V> values() {
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return inverse().keySet();
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}
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/**
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* Guaranteed to throw an exception and leave the bimap 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 V forcePut(K key, V value) {
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throw new UnsupportedOperationException();
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}
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/**
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* Serialized type for all ImmutableBiMap instances. It captures the logical
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* contents and they are reconstructed using public factory methods. This
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* ensures that the implementation types remain as implementation details.
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*
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* Since the bimap is immutable, ImmutableBiMap doesn't require special logic
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* for keeping the bimap and its inverse in sync during serialization, the way
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* AbstractBiMap does.
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*/
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private static class SerializedForm extends ImmutableMap.SerializedForm {
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SerializedForm(ImmutableBiMap<?, ?> bimap) {
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super(bimap);
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}
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@Override
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Object readResolve() {
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Builder<Object, Object> builder = new Builder<Object, Object>();
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return createMap(builder);
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}
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private static final long serialVersionUID = 0;
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}
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@Override
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Object writeReplace() {
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return new SerializedForm(this);
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}
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}
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