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 {@code final}, so a subclass
025 * can not 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 */
034public final class ImmutablePair<L, R> extends Pair<L, R> {
035
036    /** Serialization version */
037    private static final long serialVersionUID = 4954918890077093841L;
038
039    /** Left object */
040    public final L left;
041    /** Right object */
042    public final R right;
043
044    /**
045     * <p>Obtains an immutable pair of from two objects inferring the generic types.</p>
046     * 
047     * <p>This factory allows the pair to be created using inference to
048     * obtain the generic types.</p>
049     * 
050     * @param <L> the left element type
051     * @param <R> the right element type
052     * @param left  the left element, may be null
053     * @param right  the right element, may be null
054     * @return a pair formed from the two parameters, not null
055     */
056    public static <L, R> ImmutablePair<L, R> of(final L left, final R right) {
057        return new ImmutablePair<L, R>(left, right);
058    }
059
060    /**
061     * Create a new pair instance.
062     *
063     * @param left  the left value, may be null
064     * @param right  the right value, may be null
065     */
066    public ImmutablePair(final L left, final R right) {
067        super();
068        this.left = left;
069        this.right = right;
070    }
071
072    //-----------------------------------------------------------------------
073    /**
074     * {@inheritDoc}
075     */
076    @Override
077    public L getLeft() {
078        return left;
079    }
080
081    /**
082     * {@inheritDoc}
083     */
084    @Override
085    public R getRight() {
086        return right;
087    }
088
089    /**
090     * <p>Throws {@code UnsupportedOperationException}.</p>
091     * 
092     * <p>This pair is immutable, so this operation is not supported.</p>
093     *
094     * @param value  the value to set
095     * @return never
096     * @throws UnsupportedOperationException as this operation is not supported
097     */
098    @Override
099    public R setValue(final R value) {
100        throw new UnsupportedOperationException();
101    }
102
103}