    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     */
    017    package 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 the objects are threadsafe</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 1127544 2011-05-25 14:35:42Z scolebourne $
    034     */
    035    public 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(L left, 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(L left, 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        public R setValue(R value) {
    100            throw new UnsupportedOperationException();
    101        }
    102
    103    }