org.apache.commons.collections.map.LinkedMap 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.collections.map;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.AbstractList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;
import org.apache.commons.collections.iterators.UnmodifiableIterator;
import org.apache.commons.collections.iterators.UnmodifiableListIterator;
import org.apache.commons.collections.list.UnmodifiableList;
/**
* A Map implementation that maintains the order of the entries.
* In this implementation order is maintained by original insertion.
*
* This implementation improves on the JDK1.4 LinkedHashMap by adding the
* {@link org.apache.commons.collections.MapIterator MapIterator}
* functionality, additional convenience methods and allowing
* bidirectional iteration. It also implements OrderedMap.
* In addition, non-interface methods are provided to access the map by index.
*
* The orderedMapIterator() method provides direct access to a
* bidirectional iterator. The iterators from the other views can also be cast
* to OrderedIterator if required.
*
* All the available iterators can be reset back to the start by casting to
* ResettableIterator and calling reset().
*
* The implementation is also designed to be subclassed, with lots of useful
* methods exposed.
*
* Note that LinkedMap 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#synchronizedMap(Map)}. This class may throw
* exceptions when accessed by concurrent threads without synchronization.
*
* @since Commons Collections 3.0
* @version $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
*
* @author Stephen Colebourne
*/
public class LinkedMap
extends AbstractLinkedMap implements Serializable, Cloneable {
/** Serialisation version */
private static final long serialVersionUID = 9077234323521161066L;
/**
* Constructs a new empty map with default size and load factor.
*/
public LinkedMap() {
super(DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_THRESHOLD);
}
/**
* Constructs a new, empty map with the specified initial capacity.
*
* @param initialCapacity the initial capacity
* @throws IllegalArgumentException if the initial capacity is less than one
*/
public LinkedMap(int initialCapacity) {
super(initialCapacity);
}
/**
* Constructs a new, empty map with the specified initial capacity and
* load factor.
*
* @param initialCapacity the initial capacity
* @param loadFactor the load factor
* @throws IllegalArgumentException if the initial capacity is less than one
* @throws IllegalArgumentException if the load factor is less than zero
*/
public LinkedMap(int initialCapacity, float loadFactor) {
super(initialCapacity, loadFactor);
}
/**
* Constructor copying elements from another map.
*
* @param map the map to copy
* @throws NullPointerException if the map is null
*/
public LinkedMap(Map map) {
super(map);
}
//-----------------------------------------------------------------------
/**
* Clones the map without cloning the keys or values.
*
* @return a shallow clone
*/
public Object clone() {
return super.clone();
}
/**
* Write the map out using a custom routine.
*/
private void writeObject(ObjectOutputStream out) throws IOException {
out.defaultWriteObject();
doWriteObject(out);
}
/**
* Read the map in using a custom routine.
*/
private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
in.defaultReadObject();
doReadObject(in);
}
//-----------------------------------------------------------------------
/**
* Gets the key at the specified index.
*
* @param index the index to retrieve
* @return the key at the specified index
* @throws IndexOutOfBoundsException if the index is invalid
*/
public Object get(int index) {
return getEntry(index).getKey();
}
/**
* Gets the value at the specified index.
*
* @param index the index to retrieve
* @return the key at the specified index
* @throws IndexOutOfBoundsException if the index is invalid
*/
public Object getValue(int index) {
return getEntry(index).getValue();
}
/**
* Gets the index of the specified key.
*
* @param key the key to find the index of
* @return the index, or -1 if not found
*/
public int indexOf(Object key) {
key = convertKey(key);
int i = 0;
for (LinkEntry entry = header.after; entry != header; entry = entry.after, i++) {
if (isEqualKey(key, entry.key)) {
return i;
}
}
return -1;
}
/**
* Removes the element at the specified index.
*
* @param index the index of the object to remove
* @return the previous value corresponding the key,
* or null if none existed
* @throws IndexOutOfBoundsException if the index is invalid
*/
public Object remove(int index) {
return remove(get(index));
}
/**
* Gets an unmodifiable List view of the keys.
*
* The returned list is unmodifiable because changes to the values of
* the list (using {@link java.util.ListIterator#set(Object)}) will
* effectively remove the value from the list and reinsert that value at
* the end of the list, which is an unexpected side effect of changing the
* value of a list. This occurs because changing the key, changes when the
* mapping is added to the map and thus where it appears in the list.
*
* An alternative to this method is to use {@link #keySet()}.
*
* @see #keySet()
* @return The ordered list of keys.
*/
public List asList() {
return new LinkedMapList(this);
}
/**
* List view of map.
*/
static class LinkedMapList extends AbstractList {
final LinkedMap parent;
LinkedMapList(LinkedMap parent) {
this.parent = parent;
}
public int size() {
return parent.size();
}
public Object get(int index) {
return parent.get(index);
}
public boolean contains(Object obj) {
return parent.containsKey(obj);
}
public int indexOf(Object obj) {
return parent.indexOf(obj);
}
public int lastIndexOf(Object obj) {
return parent.indexOf(obj);
}
public boolean containsAll(Collection coll) {
return parent.keySet().containsAll(coll);
}
public Object remove(int index) {
throw new UnsupportedOperationException();
}
public boolean remove(Object obj) {
throw new UnsupportedOperationException();
}
public boolean removeAll(Collection coll) {
throw new UnsupportedOperationException();
}
public boolean retainAll(Collection coll) {
throw new UnsupportedOperationException();
}
public void clear() {
throw new UnsupportedOperationException();
}
public Object[] toArray() {
return parent.keySet().toArray();
}
public Object[] toArray(Object[] array) {
return parent.keySet().toArray(array);
}
public Iterator iterator() {
return UnmodifiableIterator.decorate(parent.keySet().iterator());
}
public ListIterator listIterator() {
return UnmodifiableListIterator.decorate(super.listIterator());
}
public ListIterator listIterator(int fromIndex) {
return UnmodifiableListIterator.decorate(super.listIterator(fromIndex));
}
public List subList(int fromIndexInclusive, int toIndexExclusive) {
return UnmodifiableList.decorate(super.subList(fromIndexInclusive, toIndexExclusive));
}
}
}