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Pair.java
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Pair.java
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/*
* Copyright (c) 2002-2016 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.helpers.collection;
/**
* Utility to handle pairs of objects.
*
* @param <T1> the type of the {@link #first() first value} of the pair.
* @param <T2> the type of the {@link #other() other value} of the pair.
*/
public abstract class Pair<T1, T2>
{
@SuppressWarnings( "rawtypes" )
private static final Pair EMPTY = Pair.of( null, null );
@SuppressWarnings( "unchecked" )
public static <T1, T2> Pair<T1,T2> empty()
{
return EMPTY;
}
/**
* Create a new pair of objects.
*
* @param first the first object in the pair.
* @param other the other object in the pair.
* @param <T1> the type of the first object in the pair
* @param <T2> the type of the second object in the pair
* @return a new pair of the two parameters.
*/
public static <T1, T2> Pair<T1,T2> pair( final T1 first, final T2 other )
{
return new Pair<T1,T2>()
{
@Override
public T1 first()
{
return first;
}
@Override
public T2 other()
{
return other;
}
};
}
/**
* Alias of {@link #pair(Object, Object)}.
* @param first the first object in the pair.
* @param other the other object in the pair.
* @param <T1> the type of the first object in the pair
* @param <T2> the type of the second object in the pair
* @return a new pair of the two parameters.
*/
public static <T1, T2> Pair<T1, T2> of( final T1 first, final T2 other )
{
return pair( first, other );
}
Pair()
{
// package private, limited number of subclasses
}
/**
* @return the first object in the pair.
*/
public abstract T1 first();
/**
* @return the other object in the pair.
*/
public abstract T2 other();
@Override
public String toString()
{
return "(" + first() + ", " + other() + ")";
}
@Override
public int hashCode()
{
return ( 31 * hashCode( first() ) ) | hashCode( other() );
}
@Override
public boolean equals( Object obj )
{
if ( this == obj )
{
return true;
}
if ( obj instanceof Pair )
{
@SuppressWarnings( "rawtypes" )
Pair that = (Pair) obj;
return equals( this.other(), that.other() ) && equals( this.first(), that.first() );
}
return false;
}
static int hashCode( Object obj )
{
return obj == null ? 0 : obj.hashCode();
}
static boolean equals( Object obj1, Object obj2 )
{
return ( obj1 == obj2 ) || ( obj1 != null && obj1.equals( obj2 ) );
}
}