Java tutorial
/* * Copyright (C) 2009 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.checkNotNull; import com.google.common.annotations.Beta; import com.google.common.annotations.GwtCompatible; import com.google.common.annotations.GwtIncompatible; import com.google.common.base.MoreObjects; import com.google.j2objc.annotations.Weak; import java.io.IOException; import java.io.InvalidObjectException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.util.Arrays; import java.util.Collection; import java.util.Comparator; import java.util.List; import java.util.Map; import java.util.Map.Entry; import javax.annotation.Nullable; /** * A {@link SetMultimap} whose contents will never change, with many other important properties * detailed at {@link ImmutableCollection}. * * <p>See the Guava User Guide article on <a href= * "https://github.com/google/guava/wiki/ImmutableCollectionsExplained"> * immutable collections</a>. * * @author Mike Ward * @since 2.0 */ @GwtCompatible(serializable = true, emulated = true) public class ImmutableSetMultimap<K, V> extends ImmutableMultimap<K, V> implements SetMultimap<K, V> { /** Returns the empty multimap. */ // Casting is safe because the multimap will never hold any elements. @SuppressWarnings("unchecked") public static <K, V> ImmutableSetMultimap<K, V> of() { return (ImmutableSetMultimap<K, V>) EmptyImmutableSetMultimap.INSTANCE; } /** * Returns an immutable multimap containing a single entry. */ public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1) { ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder(); builder.put(k1, v1); return builder.build(); } /** * Returns an immutable multimap containing the given entries, in order. * Repeated occurrences of an entry (according to {@link Object#equals}) after * the first are ignored. */ public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1, K k2, V v2) { ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder(); builder.put(k1, v1); builder.put(k2, v2); return builder.build(); } /** * Returns an immutable multimap containing the given entries, in order. * Repeated occurrences of an entry (according to {@link Object#equals}) after * the first are ignored. */ public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3) { ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder(); builder.put(k1, v1); builder.put(k2, v2); builder.put(k3, v3); return builder.build(); } /** * Returns an immutable multimap containing the given entries, in order. * Repeated occurrences of an entry (according to {@link Object#equals}) after * the first are ignored. */ public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) { ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder(); builder.put(k1, v1); builder.put(k2, v2); builder.put(k3, v3); builder.put(k4, v4); return builder.build(); } /** * Returns an immutable multimap containing the given entries, in order. * Repeated occurrences of an entry (according to {@link Object#equals}) after * the first are ignored. */ public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) { ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder(); builder.put(k1, v1); builder.put(k2, v2); builder.put(k3, v3); builder.put(k4, v4); builder.put(k5, v5); return builder.build(); } // looking for of() with > 5 entries? Use the builder instead. /** * Returns a new {@link Builder}. */ public static <K, V> Builder<K, V> builder() { return new Builder<K, V>(); } /** * A builder for creating immutable {@code SetMultimap} instances, especially * {@code public static final} multimaps ("constant multimaps"). Example: * <pre> {@code * * static final Multimap<String, Integer> STRING_TO_INTEGER_MULTIMAP = * new ImmutableSetMultimap.Builder<String, Integer>() * .put("one", 1) * .putAll("several", 1, 2, 3) * .putAll("many", 1, 2, 3, 4, 5) * .build();}</pre> * * <p>Builder instances can be reused; it is safe to call {@link #build} multiple * times to build multiple multimaps in series. Each multimap contains the * key-value mappings in the previously created multimaps. * * @since 2.0 */ public static final class Builder<K, V> extends ImmutableMultimap.Builder<K, V> { /** * Creates a new builder. The returned builder is equivalent to the builder * generated by {@link ImmutableSetMultimap#builder}. */ public Builder() { super(MultimapBuilder.linkedHashKeys().linkedHashSetValues().<K, V>build()); } /** * Adds a key-value mapping to the built multimap if it is not already * present. */ @Override public Builder<K, V> put(K key, V value) { builderMultimap.put(checkNotNull(key), checkNotNull(value)); return this; } /** * Adds an entry to the built multimap if it is not already present. * * @since 11.0 */ @Override public Builder<K, V> put(Entry<? extends K, ? extends V> entry) { builderMultimap.put(checkNotNull(entry.getKey()), checkNotNull(entry.getValue())); return this; } /** * {@inheritDoc} * * @since 19.0 */ @Beta @Override public Builder<K, V> putAll(Iterable<? extends Entry<? extends K, ? extends V>> entries) { super.putAll(entries); return this; } @Override public Builder<K, V> putAll(K key, Iterable<? extends V> values) { Collection<V> collection = builderMultimap.get(checkNotNull(key)); for (V value : values) { collection.add(checkNotNull(value)); } return this; } @Override public Builder<K, V> putAll(K key, V... values) { return putAll(key, Arrays.asList(values)); } @Override public Builder<K, V> putAll(Multimap<? extends K, ? extends V> multimap) { for (Entry<? extends K, ? extends Collection<? extends V>> entry : multimap.asMap().entrySet()) { putAll(entry.getKey(), entry.getValue()); } return this; } /** * {@inheritDoc} * * @since 8.0 */ @Override public Builder<K, V> orderKeysBy(Comparator<? super K> keyComparator) { this.keyComparator = checkNotNull(keyComparator); return this; } /** * Specifies the ordering of the generated multimap's values for each key. * * <p>If this method is called, the sets returned by the {@code get()} * method of the generated multimap and its {@link Multimap#asMap()} view * are {@link ImmutableSortedSet} instances. However, serialization does not * preserve that property, though it does maintain the key and value * ordering. * * @since 8.0 */ // TODO: Make serialization behavior consistent. @Override public Builder<K, V> orderValuesBy(Comparator<? super V> valueComparator) { super.orderValuesBy(valueComparator); return this; } /** * Returns a newly-created immutable set multimap. */ @Override public ImmutableSetMultimap<K, V> build() { if (keyComparator != null) { Multimap<K, V> sortedCopy = MultimapBuilder.linkedHashKeys().linkedHashSetValues().<K, V>build(); List<Map.Entry<K, Collection<V>>> entries = Ordering.from(keyComparator).<K>onKeys() .immutableSortedCopy(builderMultimap.asMap().entrySet()); for (Map.Entry<K, Collection<V>> entry : entries) { sortedCopy.putAll(entry.getKey(), entry.getValue()); } builderMultimap = sortedCopy; } return copyOf(builderMultimap, valueComparator); } } /** * Returns an immutable set multimap containing the same mappings as * {@code multimap}. The generated multimap's key and value orderings * correspond to the iteration ordering of the {@code multimap.asMap()} view. * Repeated occurrences of an entry in the multimap after the first are * ignored. * * <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 NullPointerException if any key or value in {@code multimap} is * null */ public static <K, V> ImmutableSetMultimap<K, V> copyOf(Multimap<? extends K, ? extends V> multimap) { return copyOf(multimap, null); } private static <K, V> ImmutableSetMultimap<K, V> copyOf(Multimap<? extends K, ? extends V> multimap, Comparator<? super V> valueComparator) { checkNotNull(multimap); // eager for GWT if (multimap.isEmpty() && valueComparator == null) { return of(); } if (multimap instanceof ImmutableSetMultimap) { @SuppressWarnings("unchecked") // safe since multimap is not writable ImmutableSetMultimap<K, V> kvMultimap = (ImmutableSetMultimap<K, V>) multimap; if (!kvMultimap.isPartialView()) { return kvMultimap; } } ImmutableMap.Builder<K, ImmutableSet<V>> builder = new ImmutableMap.Builder<K, ImmutableSet<V>>( multimap.asMap().size()); int size = 0; for (Entry<? extends K, ? extends Collection<? extends V>> entry : multimap.asMap().entrySet()) { K key = entry.getKey(); Collection<? extends V> values = entry.getValue(); ImmutableSet<V> set = valueSet(valueComparator, values); if (!set.isEmpty()) { builder.put(key, set); size += set.size(); } } return new ImmutableSetMultimap<K, V>(builder.build(), size, valueComparator); } /** * Returns an immutable multimap containing the specified entries. The * returned multimap iterates over keys in the order they were first * encountered in the input, and the values for each key are iterated in the * order they were encountered. If two values for the same key are * {@linkplain Object#equals equal}, the first value encountered is used. * * @throws NullPointerException if any key, value, or entry is null * @since 19.0 */ @Beta public static <K, V> ImmutableSetMultimap<K, V> copyOf( Iterable<? extends Entry<? extends K, ? extends V>> entries) { return new Builder<K, V>().putAll(entries).build(); } /** * Returned by get() when a missing key is provided. Also holds the * comparator, if any, used for values. */ private final transient ImmutableSet<V> emptySet; ImmutableSetMultimap(ImmutableMap<K, ImmutableSet<V>> map, int size, @Nullable Comparator<? super V> valueComparator) { super(map, size); this.emptySet = emptySet(valueComparator); } // views /** * Returns an immutable set of the values for the given key. If no mappings * in the multimap have the provided key, an empty immutable set is returned. * The values are in the same order as the parameters used to build this * multimap. */ @Override public ImmutableSet<V> get(@Nullable K key) { // This cast is safe as its type is known in constructor. ImmutableSet<V> set = (ImmutableSet<V>) map.get(key); return MoreObjects.firstNonNull(set, emptySet); } private transient ImmutableSetMultimap<V, K> inverse; /** * {@inheritDoc} * * <p>Because an inverse of a set multimap cannot contain multiple pairs with * the same key and value, this method returns an {@code ImmutableSetMultimap} * rather than the {@code ImmutableMultimap} specified in the {@code * ImmutableMultimap} class. * * @since 11.0 */ public ImmutableSetMultimap<V, K> inverse() { ImmutableSetMultimap<V, K> result = inverse; return (result == null) ? (inverse = invert()) : result; } private ImmutableSetMultimap<V, K> invert() { Builder<V, K> builder = builder(); for (Entry<K, V> entry : entries()) { builder.put(entry.getValue(), entry.getKey()); } ImmutableSetMultimap<V, K> invertedMultimap = builder.build(); invertedMultimap.inverse = this; return invertedMultimap; } /** * Guaranteed to throw an exception and leave the multimap unmodified. * * @throws UnsupportedOperationException always * @deprecated Unsupported operation. */ @Deprecated @Override public ImmutableSet<V> removeAll(Object key) { throw new UnsupportedOperationException(); } /** * Guaranteed to throw an exception and leave the multimap unmodified. * * @throws UnsupportedOperationException always * @deprecated Unsupported operation. */ @Deprecated @Override public ImmutableSet<V> replaceValues(K key, Iterable<? extends V> values) { throw new UnsupportedOperationException(); } private transient ImmutableSet<Entry<K, V>> entries; /** * Returns an immutable collection of all key-value pairs in the multimap. * Its iterator traverses the values for the first key, the values for the * second key, and so on. */ @Override public ImmutableSet<Entry<K, V>> entries() { ImmutableSet<Entry<K, V>> result = entries; return result == null ? (entries = new EntrySet<K, V>(this)) : result; } private static final class EntrySet<K, V> extends ImmutableSet<Entry<K, V>> { @Weak private final transient ImmutableSetMultimap<K, V> multimap; EntrySet(ImmutableSetMultimap<K, V> multimap) { this.multimap = multimap; } @Override public boolean contains(@Nullable Object object) { if (object instanceof Entry) { Entry<?, ?> entry = (Entry<?, ?>) object; return multimap.containsEntry(entry.getKey(), entry.getValue()); } return false; } @Override public int size() { return multimap.size(); } @Override public UnmodifiableIterator<Entry<K, V>> iterator() { return multimap.entryIterator(); } @Override boolean isPartialView() { return false; } } private static <V> ImmutableSet<V> valueSet(@Nullable Comparator<? super V> valueComparator, Collection<? extends V> values) { return (valueComparator == null) ? ImmutableSet.copyOf(values) : ImmutableSortedSet.copyOf(valueComparator, values); } private static <V> ImmutableSet<V> emptySet(@Nullable Comparator<? super V> valueComparator) { return (valueComparator == null) ? ImmutableSet.<V>of() : ImmutableSortedSet.<V>emptySet(valueComparator); } private static <V> ImmutableSet.Builder<V> valuesBuilder(@Nullable Comparator<? super V> valueComparator) { return (valueComparator == null) ? new ImmutableSet.Builder<V>() : new ImmutableSortedSet.Builder<V>(valueComparator); } /** * @serialData number of distinct keys, and then for each distinct key: the * key, the number of values for that key, and the key's values */ @GwtIncompatible("java.io.ObjectOutputStream") private void writeObject(ObjectOutputStream stream) throws IOException { stream.defaultWriteObject(); stream.writeObject(valueComparator()); Serialization.writeMultimap(this, stream); } @Nullable Comparator<? super V> valueComparator() { return emptySet instanceof ImmutableSortedSet ? ((ImmutableSortedSet<V>) emptySet).comparator() : null; } @GwtIncompatible("java.io.ObjectInputStream") // Serialization type safety is at the caller's mercy. @SuppressWarnings("unchecked") private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException { stream.defaultReadObject(); Comparator<Object> valueComparator = (Comparator<Object>) stream.readObject(); int keyCount = stream.readInt(); if (keyCount < 0) { throw new InvalidObjectException("Invalid key count " + keyCount); } ImmutableMap.Builder<Object, ImmutableSet<Object>> builder = ImmutableMap.builder(); int tmpSize = 0; for (int i = 0; i < keyCount; i++) { Object key = stream.readObject(); int valueCount = stream.readInt(); if (valueCount <= 0) { throw new InvalidObjectException("Invalid value count " + valueCount); } ImmutableSet.Builder<Object> valuesBuilder = valuesBuilder(valueComparator); for (int j = 0; j < valueCount; j++) { valuesBuilder.add(stream.readObject()); } ImmutableSet<Object> valueSet = valuesBuilder.build(); if (valueSet.size() != valueCount) { throw new InvalidObjectException("Duplicate key-value pairs exist for key " + key); } builder.put(key, valueSet); tmpSize += valueCount; } ImmutableMap<Object, ImmutableSet<Object>> tmpMap; try { tmpMap = builder.build(); } catch (IllegalArgumentException e) { throw (InvalidObjectException) new InvalidObjectException(e.getMessage()).initCause(e); } FieldSettersHolder.MAP_FIELD_SETTER.set(this, tmpMap); FieldSettersHolder.SIZE_FIELD_SETTER.set(this, tmpSize); FieldSettersHolder.EMPTY_SET_FIELD_SETTER.set(this, emptySet(valueComparator)); } @GwtIncompatible("not needed in emulated source.") private static final long serialVersionUID = 0; }