/*
* 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 com.google.common.annotations.GwtCompatible;
import java.util.Map;
/**
* An immutable {@link BiMap} with reliable user-specified iteration order. Does
* not permit null keys or values. An {@code ImmutableBiMap} and its inverse
* have the same iteration ordering.
*
* <p>An instance of {@code ImmutableBiMap} contains its own data and will
* <i>never</i> change. {@code ImmutableBiMap} is convenient for
* {@code public static final} maps ("constant maps") and also lets you easily
* make a "defensive copy" of a bimap provided to your class by a caller.
*
* <p><b>Note:</b> Although this class is not final, it cannot be subclassed as
* it has no public or protected constructors. Thus, instances of this class are
* guaranteed to be immutable.
*
* @author Jared Levy
* @since 2.0 (imported from Google Collections Library)
*/
@GwtCompatible(serializable = true, emulated = true)
public abstract class ImmutableBiMap<K, V> extends ImmutableMap<K, V>
implements BiMap<K, V> {
/**
* Returns the empty bimap.
*/
// 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>) EmptyImmutableBiMap.INSTANCE;
}
/**
* Returns an immutable bimap containing a single entry.
*/
public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1) {
return new SingletonImmutableBiMap<K, V>(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 new RegularImmutableBiMap<K, V>(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 new RegularImmutableBiMap<K, V>(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 new RegularImmutableBiMap<K, V>(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 new RegularImmutableBiMap<K, V>(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<K, V>();
}
/**
* 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>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 (imported from Google Collections Library)
*/
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() {}
/**
* Associates {@code key} with {@code value} in the built bimap. Duplicate
* keys or values are not allowed, and will cause {@link #build} to fail.
*/
@Override public Builder<K, V> put(K key, V value) {
super.put(key, value);
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
*/
@Override public Builder<K, V> putAll(Map<? extends K, ? extends V> map) {
super.putAll(map);
return this;
}
/**
* Returns a newly-created immutable bimap.
*
* @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:
return new RegularImmutableBiMap<K, V>(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>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
* @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(user): 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;
}
}
Entry<?, ?>[] entries = map.entrySet().toArray(EMPTY_ENTRY_ARRAY);
switch (entries.length) {
case 0:
return of();
case 1:
@SuppressWarnings("unchecked") // safe covariant cast in this context
Entry<K, V> entry = (Entry<K, V>) entries[0];
return of(entry.getKey(), entry.getValue());
default:
return new RegularImmutableBiMap<K, V>(entries);
}
}
private static final Entry<?, ?>[] EMPTY_ENTRY_ARRAY = new Entry<?, ?>[0];
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. The values are in the
* same order as the parameters used to build this map.
*/
@Override public ImmutableSet<V> values() {
return inverse().keySet();
}
/**
* Guaranteed to throw an exception and leave the bimap unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public 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.
*
* 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 extends ImmutableMap.SerializedForm {
SerializedForm(ImmutableBiMap<?, ?> bimap) {
super(bimap);
}
@Override Object readResolve() {
Builder<Object, Object> builder = new Builder<Object, Object>();
return createMap(builder);
}
private static final long serialVersionUID = 0;
}
@Override Object writeReplace() {
return new SerializedForm(this);
}
}