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/*
 * 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.math3.util;

/**
 * Generic pair.
 * 
* Although the instances of this class are immutable, it is impossible * to ensure that the references passed to the constructor will not be * modified by the caller. * * @param Key type. * @param Value type. * * @since 3.0 */ public class Pair { /** Key. */ private final K key; /** Value. */ private final V value; /** * Create an entry representing a mapping from the specified key to the * specified value. * * @param k Key (first element of the pair). * @param v Value (second element of the pair). */ public Pair(K k, V v) { key = k; value = v; } /** * Create an entry representing the same mapping as the specified entry. * * @param entry Entry to copy. */ public Pair(Pair entry) { this(entry.getKey(), entry.getValue()); } /** * Get the key. * * @return the key (first element of the pair). */ public K getKey() { return key; } /** * Get the value. * * @return the value (second element of the pair). */ public V getValue() { return value; } /** * Get the first element of the pair. * * @return the first element of the pair. * @since 3.1 */ public K getFirst() { return key; } /** * Get the second element of the pair. * * @return the second element of the pair. * @since 3.1 */ public V getSecond() { return value; } /** * Compare the specified object with this entry for equality. * * @param o Object. * @return {@code true} if the given object is also a map entry and * the two entries represent the same mapping. */ @Override public boolean equals(Object o) { if (this == o) { return true; } if (!(o instanceof Pair)) { return false; } else { Pair oP = (Pair) o; return (key == null ? oP.key == null : key.equals(oP.key)) && (value == null ? oP.value == null : value.equals(oP.value)); } } /** * Compute a hash code. * * @return the hash code value. */ @Override public int hashCode() { int result = key == null ? 0 : key.hashCode(); final int h = value == null ? 0 : value.hashCode(); result = 37 * result + h ^ (h >>> 16); return result; } /** {@inheritDoc} */ @Override public String toString() { return "[" + getKey() + ", " + getValue() + "]"; } /** * Convenience factory method that calls the * {@link #Pair(Object, Object) constructor}. * * @param the key type * @param the value type * @param k First element of the pair. * @param v Second element of the pair. * @return a new {@code Pair} containing {@code k} and {@code v}. * @since 3.3 */ public static Pair create(K k, V v) { return new Pair(k, v); } }




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