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The Apache Commons Math project is a library of lightweight, self-contained mathematics and statistics components addressing the most common practical problems not immediately available in the Java programming language or commons-lang.
/*
* 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);
}
}