/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.commons.collections4.map;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Collection;
import java.util.Map;
import java.util.Set;

import org.apache.commons.collections4.IterableMap;
import org.apache.commons.collections4.MapIterator;
import org.apache.commons.collections4.Unmodifiable;
import org.apache.commons.collections4.collection.UnmodifiableCollection;
import org.apache.commons.collections4.iterators.EntrySetMapIterator;
import org.apache.commons.collections4.iterators.UnmodifiableMapIterator;
import org.apache.commons.collections4.set.UnmodifiableSet;

Decorates another Map to ensure it can't be altered.

This class is Serializable from Commons Collections 3.1.

Attempts to modify it will result in an UnsupportedOperationException.

Type parameters:
  • <K> – the type of the keys in this map
  • <V> – the type of the values in this map
Since:3.0
/** * Decorates another <code>Map</code> to ensure it can't be altered. * <p> * This class is Serializable from Commons Collections 3.1. * </p> * <p> * Attempts to modify it will result in an UnsupportedOperationException. * </p> * * @param <K> the type of the keys in this map * @param <V> the type of the values in this map * @since 3.0 */
public final class UnmodifiableMap<K, V> extends AbstractMapDecorator<K, V> implements Unmodifiable, Serializable {
Serialization version
/** Serialization version */
private static final long serialVersionUID = 2737023427269031941L;
Factory method to create an unmodifiable map.
Params:
  • map – the map to decorate, must not be null
Type parameters:
  • <K> – the key type
  • <V> – the value type
Throws:
Returns:a new unmodifiable map
Since:4.0
/** * Factory method to create an unmodifiable map. * * @param <K> the key type * @param <V> the value type * @param map the map to decorate, must not be null * @return a new unmodifiable map * @throws NullPointerException if map is null * @since 4.0 */
public static <K, V> Map<K, V> unmodifiableMap(final Map<? extends K, ? extends V> map) { if (map instanceof Unmodifiable) { @SuppressWarnings("unchecked") // safe to upcast final Map<K, V> tmpMap = (Map<K, V>) map; return tmpMap; } return new UnmodifiableMap<>(map); } //-----------------------------------------------------------------------
Constructor that wraps (not copies).
Params:
  • map – the map to decorate, must not be null
Throws:
/** * Constructor that wraps (not copies). * * @param map the map to decorate, must not be null * @throws NullPointerException if map is null */
@SuppressWarnings("unchecked") // safe to upcast private UnmodifiableMap(final Map<? extends K, ? extends V> map) { super((Map<K, V>) map); } //-----------------------------------------------------------------------
Write the map out using a custom routine.
Params:
  • out – the output stream
Throws:
  • IOException – if an error occurs while writing to the stream
Since:3.1
/** * Write the map out using a custom routine. * * @param out the output stream * @throws IOException if an error occurs while writing to the stream * @since 3.1 */
private void writeObject(final ObjectOutputStream out) throws IOException { out.defaultWriteObject(); out.writeObject(map); }
Read the map in using a custom routine.
Params:
  • in – the input stream
Throws:
Since:3.1
/** * Read the map in using a custom routine. * * @param in the input stream * @throws IOException if an error occurs while reading from the stream * @throws ClassNotFoundException if an object read from the stream can not be loaded * @since 3.1 */
@SuppressWarnings("unchecked") private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException { in.defaultReadObject(); map = (Map<K, V>) in.readObject(); } //----------------------------------------------------------------------- @Override public void clear() { throw new UnsupportedOperationException(); } @Override public V put(final K key, final V value) { throw new UnsupportedOperationException(); } @Override public void putAll(final Map<? extends K, ? extends V> mapToCopy) { throw new UnsupportedOperationException(); } @Override public V remove(final Object key) { throw new UnsupportedOperationException(); } @Override public MapIterator<K, V> mapIterator() { if (map instanceof IterableMap) { final MapIterator<K, V> it = ((IterableMap<K, V>) map).mapIterator(); return UnmodifiableMapIterator.unmodifiableMapIterator(it); } final MapIterator<K, V> it = new EntrySetMapIterator<>(map); return UnmodifiableMapIterator.unmodifiableMapIterator(it); } @Override public Set<Map.Entry<K, V>> entrySet() { final Set<Map.Entry<K, V>> set = super.entrySet(); return UnmodifiableEntrySet.unmodifiableEntrySet(set); } @Override public Set<K> keySet() { final Set<K> set = super.keySet(); return UnmodifiableSet.unmodifiableSet(set); } @Override public Collection<V> values() { final Collection<V> coll = super.values(); return UnmodifiableCollection.unmodifiableCollection(coll); } }