001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.lang3.tuple;
018
019/**
020 * <p>An immutable pair consisting of two {@code Object} elements.</p>
021 * 
022 * <p>Although the implementation is immutable, there is no restriction on the objects
023 * that may be stored. If mutable objects are stored in the pair, then the pair
024 * itself effectively becomes mutable. The class is also not {@code final}, so a subclass
025 * could add undesirable behaviour.</p>
026 * 
027 * <p>#ThreadSafe# if both paired objects are thread-safe</p>
028 *
029 * @param <L> the left element type
030 * @param <R> the right element type
031 *
032 * @since Lang 3.0
033 * @version $Id: ImmutablePair.java 1436768 2013-01-22 07:07:42Z ggregory $
034 */
035public final class ImmutablePair<L, R> extends Pair<L, R> {
036
037    /** Serialization version */
038    private static final long serialVersionUID = 4954918890077093841L;
039
040    /** Left object */
041    public final L left;
042    /** Right object */
043    public final R right;
044
045    /**
046     * <p>Obtains an immutable pair of from two objects inferring the generic types.</p>
047     * 
048     * <p>This factory allows the pair to be created using inference to
049     * obtain the generic types.</p>
050     * 
051     * @param <L> the left element type
052     * @param <R> the right element type
053     * @param left  the left element, may be null
054     * @param right  the right element, may be null
055     * @return a pair formed from the two parameters, not null
056     */
057    public static <L, R> ImmutablePair<L, R> of(final L left, final R right) {
058        return new ImmutablePair<L, R>(left, right);
059    }
060
061    /**
062     * Create a new pair instance.
063     *
064     * @param left  the left value, may be null
065     * @param right  the right value, may be null
066     */
067    public ImmutablePair(final L left, final R right) {
068        super();
069        this.left = left;
070        this.right = right;
071    }
072
073    //-----------------------------------------------------------------------
074    /**
075     * {@inheritDoc}
076     */
077    @Override
078    public L getLeft() {
079        return left;
080    }
081
082    /**
083     * {@inheritDoc}
084     */
085    @Override
086    public R getRight() {
087        return right;
088    }
089
090    /**
091     * <p>Throws {@code UnsupportedOperationException}.</p>
092     * 
093     * <p>This pair is immutable, so this operation is not supported.</p>
094     *
095     * @param value  the value to set
096     * @return never
097     * @throws UnsupportedOperationException as this operation is not supported
098     */
099    @Override
100    public R setValue(final R value) {
101        throw new UnsupportedOperationException();
102    }
103
104}