/*
 * Copyright (c) 2016 Goldman Sachs.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Eclipse Distribution License v. 1.0 which accompany this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 */

package org.eclipse.collections.impl.map.immutable;

import java.io.Serializable;
import java.util.Collection;
import java.util.Map;
import java.util.Set;

import org.eclipse.collections.api.RichIterable;
import org.eclipse.collections.api.block.function.Function;
import org.eclipse.collections.api.block.function.Function0;
import org.eclipse.collections.api.block.function.Function2;
import org.eclipse.collections.api.block.predicate.Predicate2;
import org.eclipse.collections.api.block.procedure.Procedure;
import org.eclipse.collections.api.block.procedure.Procedure2;
import org.eclipse.collections.api.block.procedure.primitive.ObjectIntProcedure;
import org.eclipse.collections.api.map.ImmutableMap;
import org.eclipse.collections.api.tuple.Pair;
import org.eclipse.collections.impl.factory.Lists;
import org.eclipse.collections.impl.factory.Maps;
import org.eclipse.collections.impl.factory.Sets;
import org.eclipse.collections.impl.utility.LazyIterate;

This is a zero element ImmutableMap which is created by calling the Maps.immutable.empty() method.
/** * This is a zero element {@link ImmutableMap} which is created by calling the Maps.immutable.empty() method. */
final class ImmutableEmptyMap<K, V> extends AbstractImmutableMap<K, V> implements Serializable { static final ImmutableMap<?, ?> INSTANCE = new ImmutableEmptyMap<>(); private static final long serialVersionUID = 1L; @Override public int size() { return 0; } @Override public RichIterable<K> keysView() { return LazyIterate.empty(); } @Override public RichIterable<V> valuesView() { return LazyIterate.empty(); } @Override public RichIterable<Pair<K, V>> keyValuesView() { return LazyIterate.empty(); } @Override public boolean containsKey(Object key) { return false; } @Override public boolean containsValue(Object value) { return false; } @Override public V get(Object key) { return null; } @Override public Set<K> keySet() { return Sets.immutable.<K>of().castToSet(); } @Override public Collection<V> values() { return Lists.immutable.<V>empty().castToList(); } @Override public String toString() { return "{}"; } @Override public boolean equals(Object other) { if (!(other instanceof Map)) { return false; } return ((Map<K, V>) other).isEmpty(); } @Override public int hashCode() { return 0; } @Override public void forEachKeyValue(Procedure2<? super K, ? super V> procedure) { } @Override public ImmutableMap<V, K> flipUniqueValues() { return Maps.immutable.with(); } @Override public void forEachKey(Procedure<? super K> procedure) { } @Override public void forEachValue(Procedure<? super V> procedure) { } @Override public void forEachWithIndex(ObjectIntProcedure<? super V> objectIntProcedure) { } @Override public <P> void forEachWith(Procedure2<? super V, ? super P> procedure, P parameter) { } @Override public boolean isEmpty() { return true; } @Override public boolean notEmpty() { return false; } @Override public void each(Procedure<? super V> procedure) { } @Override public <A> A ifPresentApply(K key, Function<? super V, ? extends A> function) { return null; } @Override public V getIfAbsent(K key, Function0<? extends V> function) { return function.value(); } @Override public V getIfAbsentValue(K key, V value) { return value; } @Override public <P> V getIfAbsentWith( K key, Function<? super P, ? extends V> function, P parameter) { return function.valueOf(parameter); } @Override public <K2, V2> ImmutableMap<K2, V2> collect(Function2<? super K, ? super V, Pair<K2, V2>> function) { return Maps.immutable.empty(); } @Override public <R> ImmutableMap<K, R> collectValues(Function2<? super K, ? super V, ? extends R> function) { return Maps.immutable.empty(); } @Override public Pair<K, V> detect(Predicate2<? super K, ? super V> predicate) { return null; } @Override public ImmutableMap<K, V> reject(Predicate2<? super K, ? super V> predicate) { return this; } @Override public ImmutableMap<K, V> select(Predicate2<? super K, ? super V> predicate) { return this; } @Override public V getOnly() { throw new IllegalStateException("Size must be 1 but was " + this.size()); } private Object writeReplace() { return new ImmutableMapSerializationProxy<>(this); } }