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package de.lmu.ifi.dbs.elki.utilities.pairs;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2014
Ludwig-Maximilians-Universität München
Lehr- und Forschungseinheit für Datenbanksysteme
ELKI Development Team
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import de.lmu.ifi.dbs.elki.utilities.ClassGenericsUtil;
/**
* Simple class wrapping two objects.
*
* <b>Do not use this for primitive types such as {@code Integer} and
* {@code Double} - avoid the memory waste and garbage collection overhead!</b>
*
* Does not implement any "special" interfaces such as Comparable. If you need
* more complicated pairs, please use <em>domain specific</em> code, with more
* meaningful field names and comparators.
*
* @author Erich Schubert
*
* @param <FIRST> first type
* @param <SECOND> second type
*/
public class Pair<FIRST, SECOND> {
/**
* First value in pair
*/
public FIRST first;
/**
* Second value in pair
*/
public SECOND second;
/**
* Initialize pair
*
* @param first first parameter
* @param second second parameter
*/
public Pair(FIRST first, SECOND second) {
this.first = first;
this.second = second;
}
/**
* Canonical toString operator
*/
@Override
public String toString() {
return "Pair(" + (first != null ? first.toString() : "null") + ", " + (second != null ? second.toString() : "null") + ")";
}
/**
* Getter for first
*
* @return first element in pair
*/
public final FIRST getFirst() {
return first;
}
/**
* Setter for first
*
* @param first new value for first element
*/
public final void setFirst(FIRST first) {
this.first = first;
}
/**
* Getter for second element in pair
*
* @return second element in pair
*/
public final SECOND getSecond() {
return second;
}
/**
* Setter for second
*
* @param second new value for second element
*/
public final void setSecond(SECOND second) {
this.second = second;
}
/**
* Create a new array of the given size (for generics)
*
* @param <F> First class
* @param <S> Second class
* @param size array size
* @return empty array of the new type.
*/
public static final <F, S> Pair<F, S>[] newPairArray(int size) {
Class<Pair<F, S>> paircls = ClassGenericsUtil.uglyCastIntoSubclass(Pair.class);
return ClassGenericsUtil.newArrayOfNull(size, paircls);
}
/**
* Simple equals statement.
*
* This Pair equals another Object if they are identical or if the other
* Object is also a Pair and the {@link #first} and {@link #second} element of
* this Pair equal the {@link #first} and {@link #second} element,
* respectively, of the other Pair.
*
* @param obj Object to compare to
*/
@SuppressWarnings("unchecked")
@Override
public boolean equals(Object obj) {
if(this == obj) {
return true;
}
if(obj == null) {
return false;
}
if(!(obj instanceof Pair)) {
return false;
}
Pair<FIRST, SECOND> other = (Pair<FIRST, SECOND>) obj;
// Handle "null" values appropriately
if(this.first == null) {
if(other.first != null) {
return false;
}
}
else {
if(!this.first.equals(other.first)) {
return false;
}
}
if(this.second == null) {
if(other.second != null) {
return false;
}
}
else {
if(!this.second.equals(other.second)) {
return false;
}
}
return true;
}
/**
* Canonical hash function, mixing the two hash values.
*/
@Override
public final int hashCode() {
// primitive hash function mixing the two integers.
// this number does supposedly not have any factors in common with 2^32
final long prime = 2654435761L;
long result = 1;
result = prime * result + ((first == null) ? 0 : first.hashCode());
result = prime * result + ((second == null) ? 0 : second.hashCode());
return (int) result;
}
}
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