java.com.google.common.collect.ImmutableMap Maven / Gradle / Ivy
Show all versions of guava Show documentation
/*
* 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.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import static com.google.common.collect.CollectPreconditions.checkEntryNotNull;
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.concurrent.LazyInit;
import com.google.j2objc.annotations.WeakOuter;
import java.io.Serializable;
import java.util.AbstractMap;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.EnumMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.SortedMap;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.function.BiFunction;
import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.stream.Collector;
import java.util.stream.Collectors;
import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* A {@link Map} whose contents will never change, with many other important properties detailed at
* {@link ImmutableCollection}.
*
* See the Guava User Guide article on immutable collections.
*
* @author Jesse Wilson
* @author Kevin Bourrillion
* @since 2.0
*/
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // we're overriding default serialization
public abstract class ImmutableMap implements Map, Serializable {
/**
* Returns a {@link Collector} that accumulates elements into an {@code ImmutableMap} whose keys
* and values are the result of applying the provided mapping functions to the input elements.
* Entries appear in the result {@code ImmutableMap} in encounter order.
*
* If the mapped keys 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
*/
@Beta
public static Collector> toImmutableMap(
Function keyFunction,
Function valueFunction) {
return CollectCollectors.toImmutableMap(keyFunction, valueFunction);
}
/**
* Returns a {@link Collector} that accumulates elements into an {@code ImmutableMap} whose keys
* and values are the result of applying the provided mapping functions to the input elements.
*
* If the mapped keys contain duplicates (according to {@link Object#equals(Object)}), the
* values are merged using the specified merging function. Entries will appear in the encounter
* order of the first occurrence of the key.
*
* @since 21.0
*/
@Beta
public static Collector> toImmutableMap(
Function keyFunction,
Function valueFunction,
BinaryOperator mergeFunction) {
checkNotNull(keyFunction);
checkNotNull(valueFunction);
checkNotNull(mergeFunction);
return Collectors.collectingAndThen(
Collectors.toMap(keyFunction, valueFunction, mergeFunction, LinkedHashMap::new),
ImmutableMap::copyOf);
}
/**
* Returns the empty map. This map behaves and performs comparably to {@link
* Collections#emptyMap}, and is preferable mainly for consistency and maintainability of your
* code.
*/
@SuppressWarnings("unchecked")
public static ImmutableMap of() {
return (ImmutableMap) RegularImmutableMap.EMPTY;
}
/**
* Returns an immutable map containing a single entry. This map behaves and performs comparably to
* {@link Collections#singletonMap} but will not accept a null key or value. It is preferable
* mainly for consistency and maintainability of your code.
*/
public static ImmutableMap of(K k1, V v1) {
return ImmutableBiMap.of(k1, v1);
}
/**
* Returns an immutable map containing the given entries, in order.
*
* @throws IllegalArgumentException if duplicate keys are provided
*/
public static ImmutableMap of(K k1, V v1, K k2, V v2) {
return RegularImmutableMap.fromEntries(entryOf(k1, v1), entryOf(k2, v2));
}
/**
* Returns an immutable map containing the given entries, in order.
*
* @throws IllegalArgumentException if duplicate keys are provided
*/
public static ImmutableMap of(K k1, V v1, K k2, V v2, K k3, V v3) {
return RegularImmutableMap.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 are provided
*/
public static ImmutableMap of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
return RegularImmutableMap.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 are provided
*/
public static ImmutableMap of(
K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
return RegularImmutableMap.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.
/**
* Verifies that {@code key} and {@code value} are non-null, and returns a new immutable entry
* with those values.
*
* A call to {@link Entry#setValue} on the returned entry will always throw {@link
* UnsupportedOperationException}.
*/
static Entry entryOf(K key, V value) {
checkEntryNotNull(key, value);
return new AbstractMap.SimpleImmutableEntry<>(key, value);
}
/**
* Returns a new builder. The generated builder is equivalent to the builder created by the {@link
* Builder} constructor.
*/
public static Builder builder() {
return new Builder<>();
}
/**
* Returns a new builder, expecting the specified number of entries to be added.
*
* 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.
*
*
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 Builder builderWithExpectedSize(int expectedSize) {
checkNonnegative(expectedSize, "expectedSize");
return new Builder<>(expectedSize);
}
static void checkNoConflict(
boolean safe, String conflictDescription, Entry entry1, Entry entry2) {
if (!safe) {
throw conflictException(conflictDescription, entry1, entry2);
}
}
static IllegalArgumentException conflictException(
String conflictDescription, Object entry1, Object entry2) {
return new IllegalArgumentException(
"Multiple entries with same " + conflictDescription + ": " + entry1 + " and " + entry2);
}
/**
* A builder for creating immutable map instances, especially {@code public static final} maps
* ("constant maps"). Example:
*
* {@code
* static final ImmutableMap WORD_TO_INT =
* new ImmutableMap.Builder()
* .put("one", 1)
* .put("two", 2)
* .put("three", 3)
* .build();
* }
*
* For small immutable maps, the {@code ImmutableMap.of()} methods are even more
* convenient.
*
*
By default, a {@code Builder} will generate maps that iterate over entries in the order they
* were inserted into the builder, equivalently to {@code LinkedHashMap}. 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 ImmutableSortedMap} to
* sort by keys, or call {@link #orderEntriesByValue(Comparator)}, which changes this builder to
* sort entries by value.
*
*
Builder instances can be reused - it is safe to call {@link #build} multiple times to build
* multiple maps in series. Each map is a superset of the maps created before it.
*
* @since 2.0
*/
public static class Builder {
@MonotonicNonNull Comparator valueComparator;
Entry[] entries;
int size;
boolean entriesUsed;
/**
* Creates a new builder. The returned builder is equivalent to the builder generated by {@link
* ImmutableMap#builder}.
*/
public Builder() {
this(ImmutableCollection.Builder.DEFAULT_INITIAL_CAPACITY);
}
@SuppressWarnings("unchecked")
Builder(int initialCapacity) {
this.entries = new Entry[initialCapacity];
this.size = 0;
this.entriesUsed = false;
}
private void ensureCapacity(int minCapacity) {
if (minCapacity > entries.length) {
entries =
Arrays.copyOf(
entries, ImmutableCollection.Builder.expandedCapacity(entries.length, minCapacity));
entriesUsed = false;
}
}
/**
* Associates {@code key} with {@code value} in the built map. Duplicate keys are not allowed,
* and will cause {@link #build} to fail.
*/
@CanIgnoreReturnValue
public Builder put(K key, V value) {
ensureCapacity(size + 1);
Entry entry = entryOf(key, value);
// don't inline this: we want to fail atomically if key or value is null
entries[size++] = entry;
return this;
}
/**
* Adds the given {@code entry} to the map, making it immutable if necessary. Duplicate keys are
* not allowed, and will cause {@link #build} to fail.
*
* @since 11.0
*/
@CanIgnoreReturnValue
public Builder put(Entry entry) {
return put(entry.getKey(), entry.getValue());
}
/**
* Associates all of the given map's keys and values in the built map. Duplicate keys are not
* allowed, and will cause {@link #build} to fail.
*
* @throws NullPointerException if any key or value in {@code map} is null
*/
@CanIgnoreReturnValue
public Builder putAll(Map map) {
return putAll(map.entrySet());
}
/**
* Adds all of the given entries to the built map. Duplicate keys 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
public Builder putAll(Iterable> entries) {
if (entries instanceof Collection) {
ensureCapacity(size + ((Collection) entries).size());
}
for (Entry entry : entries) {
put(entry);
}
return this;
}
/**
* Configures this {@code Builder} to order entries by value according to the specified
* comparator.
*
* 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
public Builder orderEntriesByValue(Comparator valueComparator) {
checkState(this.valueComparator == null, "valueComparator was already set");
this.valueComparator = checkNotNull(valueComparator, "valueComparator");
return this;
}
@CanIgnoreReturnValue
Builder combine(Builder other) {
checkNotNull(other);
ensureCapacity(this.size + other.size);
System.arraycopy(other.entries, 0, this.entries, this.size, other.size);
this.size += other.size;
return this;
}
/*
* TODO(kevinb): Should build() and the ImmutableBiMap & ImmutableSortedMap
* versions throw an IllegalStateException instead?
*/
/**
* Returns a newly-created immutable map. The iteration order of the returned map 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 were added
*/
public ImmutableMap build() {
/*
* 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.valueFunction()));
}
switch (size) {
case 0:
return of();
case 1:
return of(entries[0].getKey(), entries[0].getValue());
default:
entriesUsed = true;
return RegularImmutableMap.fromEntryArray(size, entries);
}
}
@VisibleForTesting // only for testing JDK backed implementation
ImmutableMap buildJdkBacked() {
checkState(
valueComparator == null, "buildJdkBacked is only for testing; can't use valueComparator");
switch (size) {
case 0:
return of();
case 1:
return of(entries[0].getKey(), entries[0].getValue());
default:
entriesUsed = true;
return JdkBackedImmutableMap.create(size, entries);
}
}
}
/**
* Returns an immutable map containing the same entries as {@code map}. The returned map iterates
* over entries in the same order as the {@code entrySet} of the original map. If {@code map}
* somehow contains entries with duplicate keys (for example, if it is a {@code SortedMap} whose
* comparator is not consistent with equals), the results of this method are undefined.
*
* 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 map} is null
*/
public static ImmutableMap copyOf(Map map) {
if ((map instanceof ImmutableMap) && !(map instanceof SortedMap)) {
@SuppressWarnings("unchecked") // safe since map is not writable
ImmutableMap kvMap = (ImmutableMap) map;
if (!kvMap.isPartialView()) {
return kvMap;
}
} else if (map instanceof EnumMap) {
@SuppressWarnings("unchecked") // safe since map is not writable
ImmutableMap kvMap = (ImmutableMap) copyOfEnumMap((EnumMap) map);
return kvMap;
}
return copyOf(map.entrySet());
}
/**
* Returns an immutable map containing the specified entries. The returned map iterates over
* entries in the same order as the original iterable.
*
* @throws NullPointerException if any key, value, or entry is null
* @throws IllegalArgumentException if two entries have the same key
* @since 19.0
*/
@Beta
public static ImmutableMap copyOf(
Iterable> entries) {
@SuppressWarnings("unchecked") // we'll only be using getKey and getValue, which are covariant
Entry[] entryArray = (Entry[]) Iterables.toArray(entries, EMPTY_ENTRY_ARRAY);
switch (entryArray.length) {
case 0:
return of();
case 1:
Entry onlyEntry = entryArray[0];
return of(onlyEntry.getKey(), onlyEntry.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 RegularImmutableMap.fromEntries(entryArray);
}
}
private static , V> ImmutableMap copyOfEnumMap(
EnumMap original) {
EnumMap copy = new EnumMap<>(original);
for (Entry entry : copy.entrySet()) {
checkEntryNotNull(entry.getKey(), entry.getValue());
}
return ImmutableEnumMap.asImmutable(copy);
}
static final Entry[] EMPTY_ENTRY_ARRAY = new Entry[0];
abstract static class IteratorBasedImmutableMap extends ImmutableMap {
abstract UnmodifiableIterator> entryIterator();
Spliterator> entrySpliterator() {
return Spliterators.spliterator(
entryIterator(),
size(),
Spliterator.DISTINCT | Spliterator.NONNULL | Spliterator.IMMUTABLE | Spliterator.ORDERED);
}
@Override
ImmutableSet createKeySet() {
return new ImmutableMapKeySet<>(this);
}
@Override
ImmutableSet> createEntrySet() {
@WeakOuter
class EntrySetImpl extends ImmutableMapEntrySet {
@Override
ImmutableMap map() {
return IteratorBasedImmutableMap.this;
}
@Override
public UnmodifiableIterator> iterator() {
return entryIterator();
}
}
return new EntrySetImpl();
}
@Override
ImmutableCollection createValues() {
return new ImmutableMapValues<>(this);
}
}
ImmutableMap() {}
/**
* Guaranteed to throw an exception and leave the map unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
public final V put(K k, V v) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the map unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
public final V putIfAbsent(K key, V value) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the map unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final boolean replace(K key, V oldValue, V newValue) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the map unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final V replace(K key, V value) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the map unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final V computeIfAbsent(K key, Function mappingFunction) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the map unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final V computeIfPresent(
K key, BiFunction remappingFunction) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the map unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final V compute(K key, BiFunction remappingFunction) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the map unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final V merge(
K key, V value, BiFunction remappingFunction) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the map unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final void putAll(Map map) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the map unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final void replaceAll(BiFunction function) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the map unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final V remove(Object o) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the map unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final boolean remove(Object key, Object value) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the map unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final void clear() {
throw new UnsupportedOperationException();
}
@Override
public boolean isEmpty() {
return size() == 0;
}
@Override
public boolean containsKey(@Nullable Object key) {
return get(key) != null;
}
@Override
public boolean containsValue(@Nullable Object value) {
return values().contains(value);
}
// Overriding to mark it Nullable
@Override
public abstract V get(@Nullable Object key);
/**
* @since 21.0 (but only since 23.5 in the Android flavor).
* Note, however, that Java 8 users can call this method with any version and flavor of Guava.
*/
@Override
public final V getOrDefault(@Nullable Object key, @Nullable V defaultValue) {
V result = get(key);
return (result != null) ? result : defaultValue;
}
@LazyInit private transient ImmutableSet> entrySet;
/**
* Returns an immutable set of the mappings in this map. The iteration order is specified by the
* method used to create this map. Typically, this is insertion order.
*/
@Override
public ImmutableSet> entrySet() {
ImmutableSet> result = entrySet;
return (result == null) ? entrySet = createEntrySet() : result;
}
abstract ImmutableSet> createEntrySet();
@LazyInit private transient ImmutableSet keySet;
/**
* Returns an immutable set of the keys in this map, in the same order that they appear in {@link
* #entrySet}.
*/
@Override
public ImmutableSet keySet() {
ImmutableSet result = keySet;
return (result == null) ? keySet = createKeySet() : result;
}
/*
* This could have a good default implementation of return new ImmutableKeySet(this),
* but ProGuard can't figure out how to eliminate that default when RegularImmutableMap
* overrides it.
*/
abstract ImmutableSet createKeySet();
UnmodifiableIterator keyIterator() {
final UnmodifiableIterator> entryIterator = entrySet().iterator();
return new UnmodifiableIterator() {
@Override
public boolean hasNext() {
return entryIterator.hasNext();
}
@Override
public K next() {
return entryIterator.next().getKey();
}
};
}
Spliterator keySpliterator() {
return CollectSpliterators.map(entrySet().spliterator(), Entry::getKey);
}
@LazyInit private transient ImmutableCollection values;
/**
* Returns an immutable collection of the values in this map, in the same order that they appear
* in {@link #entrySet}.
*/
@Override
public ImmutableCollection values() {
ImmutableCollection result = values;
return (result == null) ? values = createValues() : result;
}
/*
* This could have a good default implementation of {@code return new
* ImmutableMapValues(this)}, but ProGuard can't figure out how to eliminate that default
* when RegularImmutableMap overrides it.
*/
abstract ImmutableCollection createValues();
// cached so that this.multimapView().inverse() only computes inverse once
@LazyInit private transient ImmutableSetMultimap multimapView;
/**
* Returns a multimap view of the map.
*
* @since 14.0
*/
public ImmutableSetMultimap asMultimap() {
if (isEmpty()) {
return ImmutableSetMultimap.of();
}
ImmutableSetMultimap result = multimapView;
return (result == null)
? (multimapView =
new ImmutableSetMultimap<>(new MapViewOfValuesAsSingletonSets(), size(), null))
: result;
}
@WeakOuter
private final class MapViewOfValuesAsSingletonSets
extends IteratorBasedImmutableMap> {
@Override
public int size() {
return ImmutableMap.this.size();
}
@Override
ImmutableSet createKeySet() {
return ImmutableMap.this.keySet();
}
@Override
public boolean containsKey(@Nullable Object key) {
return ImmutableMap.this.containsKey(key);
}
@Override
public ImmutableSet get(@Nullable Object key) {
V outerValue = ImmutableMap.this.get(key);
return (outerValue == null) ? null : ImmutableSet.of(outerValue);
}
@Override
boolean isPartialView() {
return ImmutableMap.this.isPartialView();
}
@Override
public int hashCode() {
// ImmutableSet.of(value).hashCode() == value.hashCode(), so the hashes are the same
return ImmutableMap.this.hashCode();
}
@Override
boolean isHashCodeFast() {
return ImmutableMap.this.isHashCodeFast();
}
@Override
UnmodifiableIterator>> entryIterator() {
final Iterator> backingIterator = ImmutableMap.this.entrySet().iterator();
return new UnmodifiableIterator>>() {
@Override
public boolean hasNext() {
return backingIterator.hasNext();
}
@Override
public Entry> next() {
final Entry backingEntry = backingIterator.next();
return new AbstractMapEntry>() {
@Override
public K getKey() {
return backingEntry.getKey();
}
@Override
public ImmutableSet getValue() {
return ImmutableSet.of(backingEntry.getValue());
}
};
}
};
}
}
@Override
public boolean equals(@Nullable Object object) {
return Maps.equalsImpl(this, object);
}
abstract boolean isPartialView();
@Override
public int hashCode() {
return Sets.hashCodeImpl(entrySet());
}
boolean isHashCodeFast() {
return false;
}
@Override
public String toString() {
return Maps.toStringImpl(this);
}
/**
* Serialized type for all ImmutableMap instances. It captures the logical contents and they are
* reconstructed using public factory methods. This ensures that the implementation types remain
* as implementation details.
*/
static class SerializedForm implements Serializable {
private final Object[] keys;
private final Object[] values;
SerializedForm(ImmutableMap map) {
keys = new Object[map.size()];
values = new Object[map.size()];
int i = 0;
for (Entry entry : map.entrySet()) {
keys[i] = entry.getKey();
values[i] = entry.getValue();
i++;
}
}
Object readResolve() {
Builder builder = new Builder<>(keys.length);
return createMap(builder);
}
Object createMap(Builder builder) {
for (int i = 0; i < keys.length; i++) {
builder.put(keys[i], values[i]);
}
return builder.build();
}
private static final long serialVersionUID = 0;
}
Object writeReplace() {
return new SerializedForm(this);
}
}