org.apache.commons.collections4.map.LazySortedMap Maven / Gradle / Ivy
/*
* 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.util.Comparator;
import java.util.SortedMap;
import org.apache.commons.collections4.Factory;
import org.apache.commons.collections4.Transformer;
/**
* Decorates another SortedMap
to create objects in the map on demand.
*
* When the {@link #get(Object)} method is called with a key that does not
* exist in the map, the factory is used to create the object. The created
* object will be added to the map using the requested key.
*
* For instance:
*
* Factory<Date> factory = new Factory<Date>() {
* public Date create() {
* return new Date();
* }
* }
* SortedMap<String, Date> lazy =
* LazySortedMap.lazySortedMap(new HashMap<String, Date>(), factory);
* Date date = lazy.get("NOW");
*
*
* After the above code is executed, date
will refer to
* a new Date
instance. Furthermore, that Date
* instance is mapped to the "NOW" key in the map.
*
* Note that LazySortedMap 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 LazySortedMap extends LazyMap implements SortedMap {
/** Serialization version */
private static final long serialVersionUID = 2715322183617658933L;
/**
* Factory method to create a lazily instantiated sorted map.
*
* @param the key type
* @param the value type
* @param map the map to decorate, must not be null
* @param factory the factory to use, must not be null
* @return a new lazy sorted map
* @throws NullPointerException if map or factory is null
* @since 4.0
*/
public static LazySortedMap lazySortedMap(final SortedMap map,
final Factory factory) {
return new LazySortedMap<>(map, factory);
}
/**
* Factory method to create a lazily instantiated sorted map.
*
* @param the key type
* @param the value type
* @param map the map to decorate, must not be null
* @param factory the factory to use, must not be null
* @return a new lazy sorted map
* @throws NullPointerException if map or factory is null
* @since 4.0
*/
public static LazySortedMap lazySortedMap(final SortedMap map,
final Transformer factory) {
return new LazySortedMap<>(map, factory);
}
//-----------------------------------------------------------------------
/**
* Constructor that wraps (not copies).
*
* @param map the map to decorate, must not be null
* @param factory the factory to use, must not be null
* @throws NullPointerException if map or factory is null
*/
protected LazySortedMap(final SortedMap map, final Factory factory) {
super(map, factory);
}
/**
* Constructor that wraps (not copies).
*
* @param map the map to decorate, must not be null
* @param factory the factory to use, must not be null
* @throws NullPointerException if map or factory is null
*/
protected LazySortedMap(final SortedMap map, final Transformer factory) {
super(map, factory);
}
//-----------------------------------------------------------------------
/**
* Gets the map being decorated.
*
* @return the decorated map
*/
protected SortedMap getSortedMap() {
return (SortedMap) map;
}
//-----------------------------------------------------------------------
@Override
public K firstKey() {
return getSortedMap().firstKey();
}
@Override
public K lastKey() {
return getSortedMap().lastKey();
}
@Override
public Comparator comparator() {
return getSortedMap().comparator();
}
@Override
public SortedMap subMap(final K fromKey, final K toKey) {
final SortedMap map = getSortedMap().subMap(fromKey, toKey);
return new LazySortedMap<>(map, factory);
}
@Override
public SortedMap headMap(final K toKey) {
final SortedMap map = getSortedMap().headMap(toKey);
return new LazySortedMap<>(map, factory);
}
@Override
public SortedMap tailMap(final K fromKey) {
final SortedMap map = getSortedMap().tailMap(fromKey);
return new LazySortedMap<>(map, factory);
}
}