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/*
* Copyright (C) 2007 Google Inc.
*
* 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.inject.internal.util;
import com.google.inject.internal.Nullable;
import java.util.Collections;
import java.util.HashMap;
import java.util.IdentityHashMap;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.TreeMap;
/**
* Static utility methods pertaining to {@link Map} instances. Also see this
* class's counterparts {@link Lists} and {@link Sets}.
*
* @author Kevin Bourrillion
* @author Mike Bostock
* @author Isaac Shum
*/
public final class Maps {
private Maps() {}
/**
* Creates a {@code HashMap} instance.
*
* <p><b>Note:</b> if you don't actually need the resulting map to be mutable,
* use {@link Collections#emptyMap} instead.
*
* @return a new, empty {@code HashMap}
*/
public static <K, V> HashMap<K, V> newHashMap() {
return new HashMap<K, V>();
}
/**
* Creates an insertion-ordered {@code LinkedHashMap} instance.
*
* @return a new, empty {@code LinkedHashMap}
*/
public static <K, V> LinkedHashMap<K, V> newLinkedHashMap() {
return new LinkedHashMap<K, V>();
}
/**
* Creates a {@code TreeMap} instance using the natural ordering of its
* elements.
*
* @return a new, empty {@code TreeMap}
*/
@SuppressWarnings("unchecked") // allow ungenerified Comparable types
public static <K extends Comparable, V> TreeMap<K, V> newTreeMap() {
return new TreeMap<K, V>();
}
/**
* Creates an {@code IdentityHashMap} instance.
*
* @return a new, empty {@code IdentityHashMap}
*/
public static <K, V> IdentityHashMap<K, V> newIdentityHashMap() {
return new IdentityHashMap<K, V>();
}
/**
* Returns an immutable map entry with the specified key and value. The {@link
* Entry#setValue} operation throws an {@link UnsupportedOperationException}.
*
* <p>The returned entry is serializable.
*
* @param key the key to be associated with the returned entry
* @param value the value to be associated with the returned entry
*/
public static <K, V> Entry<K, V> immutableEntry(
@Nullable final K key, @Nullable final V value) {
return new ImmutableEntry<K, V>(key, value);
}
}
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