ImmutableBiMap.java
/*
* Copyright (C) 2008 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.collect;
import static com.google.common.base.Preconditions.checkState;
import static com.google.common.collect.CollectPreconditions.checkNonnegative;
import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.DoNotCall;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Map;
import java.util.function.Function;
import java.util.stream.Collector;
import java.util.stream.Collectors;
/**
* A {@link BiMap} whose contents will never change, with many other important properties detailed
* at {@link ImmutableCollection}.
*
* @author Jared Levy
* @since 2.0
*/
@GwtCompatible(serializable = true, emulated = true)
public abstract class ImmutableBiMap<K, V> extends ImmutableBiMapFauxverideShim<K, V>
implements BiMap<K, V> {
/**
* Returns a {@link Collector} that accumulates elements into an {@code ImmutableBiMap} whose keys
* and values are the result of applying the provided mapping functions to the input elements.
* Entries appear in the result {@code ImmutableBiMap} in encounter order.
*
* <p>If the mapped keys or values contain duplicates (according to {@link Object#equals(Object)},
* an {@code IllegalArgumentException} is thrown when the collection operation is performed. (This
* differs from the {@code Collector} returned by {@link Collectors#toMap(Function, Function)},
* which throws an {@code IllegalStateException}.)
*
* @since 21.0
*/
public static <T, K, V> Collector<T, ?, ImmutableBiMap<K, V>> toImmutableBiMap(
Function<? super T, ? extends K> keyFunction,
Function<? super T, ? extends V> valueFunction) {
return CollectCollectors.toImmutableBiMap(keyFunction, valueFunction);
}
/**
* Returns the empty bimap.
*
* <p><b>Performance note:</b> the instance returned is a singleton.
*/
// Casting to any type is safe because the set will never hold any elements.
@SuppressWarnings("unchecked")
public static <K, V> ImmutableBiMap<K, V> of() {
return (ImmutableBiMap<K, V>) RegularImmutableBiMap.EMPTY;
}
/** Returns an immutable bimap containing a single entry. */
public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1) {
return new SingletonImmutableBiMap<>(k1, v1);
}
/**
* Returns an immutable map containing the given entries, in order.
*
* @throws IllegalArgumentException if duplicate keys or values are added
*/
public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2) {
return RegularImmutableBiMap.fromEntries(entryOf(k1, v1), entryOf(k2, v2));
}
/**
* Returns an immutable map containing the given entries, in order.
*
* @throws IllegalArgumentException if duplicate keys or values are added
*/
public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3) {
return RegularImmutableBiMap.fromEntries(entryOf(k1, v1), entryOf(k2, v2), entryOf(k3, v3));
}
/**
* Returns an immutable map containing the given entries, in order.
*
* @throws IllegalArgumentException if duplicate keys or values are added
*/
public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
return RegularImmutableBiMap.fromEntries(
entryOf(k1, v1), entryOf(k2, v2), entryOf(k3, v3), entryOf(k4, v4));
}
/**
* Returns an immutable map containing the given entries, in order.
*
* @throws IllegalArgumentException if duplicate keys or values are added
*/
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) {
return RegularImmutableBiMap.fromEntries(
entryOf(k1, v1), entryOf(k2, v2), entryOf(k3, v3), entryOf(k4, v4), entryOf(k5, v5));
}
// looking for of() with > 5 entries? Use the builder instead.
/**
* Returns a new builder. The generated builder is equivalent to the builder created by the {@link
* Builder} constructor.
*/
public static <K, V> Builder<K, V> builder() {
return new Builder<>();
}
/**
* Returns a new builder, expecting the specified number of entries to be added.
*
* <p>If {@code expectedSize} is exactly the number of entries added to the builder before {@link
* Builder#build} is called, the builder is likely to perform better than an unsized {@link
* #builder()} would have.
*
* <p>It is not specified if any performance benefits apply if {@code expectedSize} is close to,
* but not exactly, the number of entries added to the builder.
*
* @since 23.1
*/
@Beta
public static <K, V> Builder<K, V> builderWithExpectedSize(int expectedSize) {
checkNonnegative(expectedSize, "expectedSize");
return new Builder<>(expectedSize);
}
/**
* A builder for creating immutable bimap instances, especially {@code public static final} bimaps
* ("constant bimaps"). Example:
*
* <pre>{@code
* static final ImmutableBiMap<String, Integer> WORD_TO_INT =
* new ImmutableBiMap.Builder<String, Integer>()
* .put("one", 1)
* .put("two", 2)
* .put("three", 3)
* .build();
* }</pre>
*
* <p>For <i>small</i> immutable bimaps, the {@code ImmutableBiMap.of()} methods are even more
* convenient.
*
* <p>By default, a {@code Builder} will generate bimaps that iterate over entries in the order
* they were inserted into the builder. For example, in the above example, {@code
* WORD_TO_INT.entrySet()} is guaranteed to iterate over the entries in the order {@code "one"=1,
* "two"=2, "three"=3}, and {@code keySet()} and {@code values()} respect the same order. If you
* want a different order, consider using {@link #orderEntriesByValue(Comparator)}, which changes
* this builder to sort entries by value.
*
* <p>Builder instances can be reused - it is safe to call {@link #build} multiple times to build
* multiple bimaps in series. Each bimap is a superset of the bimaps created before it.
*
* @since 2.0
*/
public static final class Builder<K, V> extends ImmutableMap.Builder<K, V> {
/**
* Creates a new builder. The returned builder is equivalent to the builder generated by {@link
* ImmutableBiMap#builder}.
*/
public Builder() {}
Builder(int size) {
super(size);
}
/**
* Associates {@code key} with {@code value} in the built bimap. Duplicate keys or values are
* not allowed, and will cause {@link #build} to fail.
*/
@CanIgnoreReturnValue
@Override
public Builder<K, V> put(K key, V value) {
super.put(key, value);
return this;
}
/**
* Adds the given {@code entry} to the bimap. Duplicate keys or values are not allowed, and will
* cause {@link #build} to fail.
*
* @since 19.0
*/
@CanIgnoreReturnValue
@Override
public Builder<K, V> put(Entry<? extends K, ? extends V> entry) {
super.put(entry);
return this;
}
/**
* Associates all of the given map's keys and values in the built bimap. Duplicate keys or
* values are not allowed, and will cause {@link #build} to fail.
*
* @throws NullPointerException if any key or value in {@code map} is null
*/
@CanIgnoreReturnValue
@Override
public Builder<K, V> putAll(Map<? extends K, ? extends V> map) {
super.putAll(map);
return this;
}
/**
* Adds all of the given entries to the built bimap. Duplicate keys or values are not allowed,
* and will cause {@link #build} to fail.
*
* @throws NullPointerException if any key, value, or entry is null
* @since 19.0
*/
@CanIgnoreReturnValue
@Beta
@Override
public Builder<K, V> putAll(Iterable<? extends Entry<? extends K, ? extends V>> entries) {
super.putAll(entries);
return this;
}
/**
* Configures this {@code Builder} to order entries by value according to the specified
* comparator.
*
* <p>The sort order is stable, that is, if two entries have values that compare as equivalent,
* the entry that was inserted first will be first in the built map's iteration order.
*
* @throws IllegalStateException if this method was already called
* @since 19.0
*/
@CanIgnoreReturnValue
@Beta
@Override
public Builder<K, V> orderEntriesByValue(Comparator<? super V> valueComparator) {
super.orderEntriesByValue(valueComparator);
return this;
}
@Override
@CanIgnoreReturnValue
Builder<K, V> combine(ImmutableMap.Builder<K, V> builder) {
super.combine(builder);
return this;
}
/**
* Returns a newly-created immutable bimap. The iteration order of the returned bimap is the
* order in which entries were inserted into the builder, unless {@link #orderEntriesByValue}
* was called, in which case entries are sorted by value.
*
* @throws IllegalArgumentException if duplicate keys or values were added
*/
@Override
public ImmutableBiMap<K, V> build() {
switch (size) {
case 0:
return of();
case 1:
return of(entries[0].getKey(), entries[0].getValue());
default:
/*
* If entries is full, or if hash flooding is detected, then this implementation may end
* up using the entries array directly and writing over the entry objects with
* non-terminal entries, but this is safe; if this Builder is used further, it will grow
* the entries array (so it can't affect the original array), and future build() calls
* will always copy any entry objects that cannot be safely reused.
*/
if (valueComparator != null) {
if (entriesUsed) {
entries = Arrays.copyOf(entries, size);
}
Arrays.sort(
entries,
0,
size,
Ordering.from(valueComparator).onResultOf(Maps.<V>valueFunction()));
}
entriesUsed = true;
return RegularImmutableBiMap.fromEntryArray(size, entries);
}
}
@Override
@VisibleForTesting
ImmutableBiMap<K, V> buildJdkBacked() {
checkState(
valueComparator == null,
"buildJdkBacked is for tests only, doesn't support orderEntriesByValue");
switch (size) {
case 0:
return of();
case 1:
return of(entries[0].getKey(), entries[0].getValue());
default:
entriesUsed = true;
return RegularImmutableBiMap.fromEntryArray(size, entries);
}
}
}
/**
* Returns an immutable bimap containing the same entries as {@code map}. If {@code map} somehow
* contains entries with duplicate keys (for example, if it is a {@code SortedMap} whose
* comparator is not <i>consistent with equals</i>), the results of this method are undefined.
*
* <p>The returned {@code BiMap} iterates over entries in the same order as the {@code entrySet}
* of the original map.
*
* <p>Despite the method name, this method attempts to avoid actually copying the data when it is
* safe to do so. The exact circumstances under which a copy will or will not be performed are
* undocumented and subject to change.
*
* @throws IllegalArgumentException if two keys have the same value or two values have the same
* key
* @throws NullPointerException if any key or value in {@code map} is null
*/
public static <K, V> ImmutableBiMap<K, V> copyOf(Map<? extends K, ? extends V> map) {
if (map instanceof ImmutableBiMap) {
@SuppressWarnings("unchecked") // safe since map is not writable
ImmutableBiMap<K, V> bimap = (ImmutableBiMap<K, V>) map;
// TODO(lowasser): if we need to make a copy of a BiMap because the
// forward map is a view, don't make a copy of the non-view delegate map
if (!bimap.isPartialView()) {
return bimap;
}
}
return copyOf(map.entrySet());
}
/**
* Returns an immutable bimap containing the given entries. The returned bimap iterates over
* entries in the same order as the original iterable.
*
* @throws IllegalArgumentException if two keys have the same value or two values have the same
* key
* @throws NullPointerException if any key, value, or entry is null
* @since 19.0
*/
@Beta
public static <K, V> ImmutableBiMap<K, V> copyOf(
Iterable<? extends Entry<? extends K, ? extends V>> entries) {
@SuppressWarnings("unchecked") // we'll only be using getKey and getValue, which are covariant
Entry<K, V>[] entryArray = (Entry<K, V>[]) Iterables.toArray(entries, EMPTY_ENTRY_ARRAY);
switch (entryArray.length) {
case 0:
return of();
case 1:
Entry<K, V> entry = entryArray[0];
return of(entry.getKey(), entry.getValue());
default:
/*
* The current implementation will end up using entryArray directly, though it will write
* over the (arbitrary, potentially mutable) Entry objects actually stored in entryArray.
*/
return RegularImmutableBiMap.fromEntries(entryArray);
}
}
ImmutableBiMap() {}
/**
* {@inheritDoc}
*
* <p>The inverse of an {@code ImmutableBiMap} is another {@code ImmutableBiMap}.
*/
@Override
public abstract ImmutableBiMap<V, K> inverse();
/**
* Returns an immutable set of the values in this map, in the same order they appear in {@link
* #entrySet}.
*/
@Override
public ImmutableSet<V> values() {
return inverse().keySet();
}
@Override
final ImmutableSet<V> createValues() {
throw new AssertionError("should never be called");
}
/**
* Guaranteed to throw an exception and leave the bimap unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
@DoNotCall("Always throws UnsupportedOperationException")
public final V forcePut(K key, V value) {
throw new UnsupportedOperationException();
}
/**
* Serialized type for all ImmutableBiMap instances. It captures the logical contents and they are
* reconstructed using public factory methods. This ensures that the implementation types remain
* as implementation details.
*
* <p>Since the bimap is immutable, ImmutableBiMap doesn't require special logic for keeping the
* bimap and its inverse in sync during serialization, the way AbstractBiMap does.
*/
private static class SerializedForm<K, V> extends ImmutableMap.SerializedForm<K, V> {
SerializedForm(ImmutableBiMap<K, V> bimap) {
super(bimap);
}
@Override
Builder<K, V> makeBuilder(int size) {
return new Builder<>(size);
}
private static final long serialVersionUID = 0;
}
@Override
Object writeReplace() {
return new SerializedForm<>(this);
}
}