/*******************************************************************************
* Copyright 2014 Analog Devices, Inc.
*
* Licensed 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 com.analog.lyric.collect;
import java.io.Serializable;
import java.util.Collection;
import java.util.Comparator;
import java.util.SortedSet;
import net.jcip.annotations.Immutable;
import org.eclipse.jdt.annotation.NonNullByDefault;
import org.eclipse.jdt.annotation.Nullable;
/**
*
* @author Christopher Barber
* @since 0.05
*/
public final class Comparators
{
private Comparators() {} // Prevent instantiation
@Immutable
@NonNullByDefault(false)
private static enum LexicalIntArrayComparator implements Comparator<int[]>, Serializable
{
INSTANCE;
@Override
public int compare(int[] array1, int[] array2)
{
int diff = array1.length - array2.length;
if (diff == 0)
{
for (int i = 0, end = array1.length; i < end; ++i)
{
int val1 = array1[i], val2 = array2[i];
if (val1 != val2)
{
diff = val1 < val2 ? -1 : 1;
break;
}
}
}
return diff;
}
}
@Immutable
@NonNullByDefault(false)
private static enum ReverseLexicalIntArrayComparator implements Comparator<int[]>, Serializable
{
INSTANCE;
@Override
public int compare(int[] array1, int[] array2)
{
int diff = array1.length - array2.length;
if (diff == 0)
{
for (int i = array1.length; --i >= 0;)
{
int val1 = array1[i], val2 = array2[i];
if (val1 != val2)
{
diff = val1 < val2 ? -1 : 1;
break;
}
}
}
return diff;
}
}
/**
* Returns a comparator for int arrays that compares arrays in reverse lexicographical order, which
* compares elements from the last index backward (e.g. {@code [1,2,3]} is after {@code [1,3,2]}).
* If arrays are of different length, the shorter array comes first.
*
* @see #lexicalIntArray()
*/
public static Comparator<int[]> reverseLexicalIntArray()
{
return ReverseLexicalIntArrayComparator.INSTANCE;
}
/**
* Returns a comparator for int arrays that compares arrays in lexicographical (aka "dictionary") order
* (e.g. {@code [1,2,3]} is before {@code [1,3,2]}). If arrays are of different length, the shorter array comes
* first.
*
* @see #reverseLexicalIntArray()
*/
public static Comparator<int[]> lexicalIntArray()
{
return LexicalIntArrayComparator.INSTANCE;
}
/**
* Returns comparator used by collection.
*
* <If collection is a {@link SortedSet} returns {@link SortedSet#comparator()}, else returns null.
*/
public static @Nullable <T> Comparator<? super T> fromCollection(Collection<? extends T> collection)
{
@SuppressWarnings("unchecked")
Comparator<? super T> comparator = collection instanceof SortedSet ?
(Comparator<? super T>) ((SortedSet<? extends T>)collection).comparator() : null ;
return comparator;
}
}