org.apache.commons.collections4.bag.TreeBag 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.bag;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Collection;
import java.util.Comparator;
import java.util.SortedMap;
import java.util.TreeMap;
import org.apache.commons.collections4.SortedBag;
/**
* Implements {@link SortedBag}, using a {@link TreeMap} to provide the data storage.
* This is the standard implementation of a sorted bag.
*
* Order will be maintained among the bag members and can be viewed through the iterator.
*
* A {@link org.apache.commons.collections4.Bag Bag} stores each object in the collection
* together with a count of occurrences. Extra methods on the interface allow multiple
* copies of an object to be added or removed at once. It is important to read the interface
* javadoc carefully as several methods violate the {@link Collection} interface specification.
*
* @param the type of elements in this bag
* @since 3.0 (previously in main package v2.0)
*/
public class TreeBag extends AbstractMapBag implements SortedBag, Serializable {
/** Serial version lock */
private static final long serialVersionUID = -7740146511091606676L;
/**
* Constructs an empty {@link TreeBag}.
*/
public TreeBag() {
super(new TreeMap());
}
/**
* Constructs an empty bag that maintains order on its unique representative
* members according to the given {@link Comparator}.
*
* @param comparator the comparator to use
*/
public TreeBag(final Comparator comparator) {
super(new TreeMap(comparator));
}
/**
* Constructs a {@link TreeBag} containing all the members of the
* specified collection.
*
* @param coll the collection to copy into the bag
*/
public TreeBag(final Collection coll) {
this();
addAll(coll);
}
//-----------------------------------------------------------------------
/**
* {@inheritDoc}
*
* @throws IllegalArgumentException if the object to be added does not implement
* {@link Comparable} and the {@link TreeBag} is using natural ordering
* @throws NullPointerException if the specified key is null and this bag uses
* natural ordering, or its comparator does not permit null keys
*/
@Override
public boolean add(final E object) {
if(comparator() == null && !(object instanceof Comparable)) {
if (object == null) {
throw new NullPointerException();
}
throw new IllegalArgumentException("Objects of type " + object.getClass() + " cannot be added to " +
"a naturally ordered TreeBag as it does not implement Comparable");
}
return super.add(object);
}
//-----------------------------------------------------------------------
@Override
public E first() {
return getMap().firstKey();
}
@Override
public E last() {
return getMap().lastKey();
}
@Override
public Comparator comparator() {
return getMap().comparator();
}
@Override
protected SortedMap getMap() {
return (SortedMap) super.getMap();
}
//-----------------------------------------------------------------------
/**
* Write the bag 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(comparator());
super.doWriteObject(out);
}
/**
* Read the bag 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
*/
private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
in.defaultReadObject();
@SuppressWarnings("unchecked") // This will fail at runtime if the stream is incorrect
final Comparator comp = (Comparator) in.readObject();
super.doReadObject(new TreeMap(comp), in);
}
}