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The Apache Commons Collections package contains types that extend and augment the Java Collections Framework.
/*
* 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 java.util.SortedMap;
import org.apache.commons.collections4.BoundedMap;
import org.apache.commons.collections4.CollectionUtils;
import org.apache.commons.collections4.collection.UnmodifiableCollection;
import org.apache.commons.collections4.set.UnmodifiableSet;
/**
* Decorates another SortedMap to fix the size blocking add/remove.
*
* Any action that would change the size of the map is disallowed.
* The put method is allowed to change the value associated with an existing
* key however.
*
*
* If trying to remove or clear the map, an UnsupportedOperationException is
* thrown. If trying to put a new mapping into the map, an
* IllegalArgumentException is thrown. This is because the put method can
* succeed if the mapping's key already exists in the map, so the put method
* is not always unsupported.
*
*
* Note that FixedSizeSortedMap is not synchronized and is not thread-safe.
* If you wish to use this map from multiple threads concurrently, you must use
* appropriate synchronization. The simplest approach is to wrap this map
* using {@link java.util.Collections#synchronizedSortedMap}. This class may throw
* exceptions when accessed by concurrent threads without synchronization.
*
*
* This class is Serializable from Commons Collections 3.1.
*
*
* @param the type of the keys in this map
* @param the type of the values in this map
* @since 3.0
*/
public class FixedSizeSortedMap
extends AbstractSortedMapDecorator
implements BoundedMap, Serializable {
/** Serialization version */
private static final long serialVersionUID = 3126019624511683653L;
/**
* Factory method to create a fixed size sorted map.
*
* @param the key type
* @param the value type
* @param map the map to decorate, must not be null
* @return a new fixed size sorted map
* @throws NullPointerException if map is null
* @since 4.0
*/
public static FixedSizeSortedMap fixedSizeSortedMap(final SortedMap map) {
return new FixedSizeSortedMap<>(map);
}
//-----------------------------------------------------------------------
/**
* Constructor that wraps (not copies).
*
* @param map the map to decorate, must not be null
* @throws NullPointerException if map is null
*/
protected FixedSizeSortedMap(final SortedMap map) {
super(map);
}
/**
* Gets the map being decorated.
*
* @return the decorated map
*/
protected SortedMap getSortedMap() {
return (SortedMap) map;
}
//-----------------------------------------------------------------------
/**
* Write the map out using a custom routine.
*
* @param out the output stream
* @throws IOException if an error occurs while writing to the stream
*/
private void writeObject(final ObjectOutputStream out) throws IOException {
out.defaultWriteObject();
out.writeObject(map);
}
/**
* 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
*/
@SuppressWarnings("unchecked") // (1) should only fail if input stream is incorrect
private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
in.defaultReadObject();
map = (Map) in.readObject(); // (1)
}
//-----------------------------------------------------------------------
@Override
public V put(final K key, final V value) {
if (map.containsKey(key) == false) {
throw new IllegalArgumentException("Cannot put new key/value pair - Map is fixed size");
}
return map.put(key, value);
}
@Override
public void putAll(final Map mapToCopy) {
if (CollectionUtils.isSubCollection(mapToCopy.keySet(), keySet())) {
throw new IllegalArgumentException("Cannot put new key/value pair - Map is fixed size");
}
map.putAll(mapToCopy);
}
@Override
public void clear() {
throw new UnsupportedOperationException("Map is fixed size");
}
@Override
public V remove(final Object key) {
throw new UnsupportedOperationException("Map is fixed size");
}
@Override
public Set> entrySet() {
return UnmodifiableSet.unmodifiableSet(map.entrySet());
}
@Override
public Set keySet() {
return UnmodifiableSet.unmodifiableSet(map.keySet());
}
@Override
public Collection values() {
return UnmodifiableCollection.unmodifiableCollection(map.values());
}
//-----------------------------------------------------------------------
@Override
public SortedMap subMap(final K fromKey, final K toKey) {
return new FixedSizeSortedMap<>(getSortedMap().subMap(fromKey, toKey));
}
@Override
public SortedMap headMap(final K toKey) {
return new FixedSizeSortedMap<>(getSortedMap().headMap(toKey));
}
@Override
public SortedMap tailMap(final K fromKey) {
return new FixedSizeSortedMap<>(getSortedMap().tailMap(fromKey));
}
@Override
public boolean isFull() {
return true;
}
@Override
public int maxSize() {
return size();
}
}