Removing ComparatorUtils. I don't think min/max(Obj,Obj,Comparator) are the most useful methods, and I'm not sure we need the static factory methods to instantiate the comparators.
git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@1161378 13f79535-47bb-0310-9956-ffa450edef68
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Henri Yandell
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/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.apache.commons.lang3.compare;
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import java.util.Collection;
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import java.util.Comparator;
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/**
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* Provides convenient static utility methods for <Code>Comparator</Code>
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* objects.
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* <p>
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* Most of the functionality in this class can also be found in the
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* <code>comparators</code> package. This class merely provides a
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* convenient central place if you have use for more than one class
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* in the <code>comparators</code> subpackage.
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*
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* @since Commons Collections 2.1
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* @version $Revision$ $Date$
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*/
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public class ComparatorUtils {
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/**
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* ComparatorUtils should not normally be instantiated.
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*/
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public ComparatorUtils() {
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}
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/**
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* Comparator for natural sort order.
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*
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* @see ComparableComparator#getInstance
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*/
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@SuppressWarnings("unchecked")
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public static final Comparator NATURAL_COMPARATOR = ComparableComparator.<Comparable>comparableComparator();
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/**
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* Gets a comparator that uses the natural order of the objects.
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*
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* @return a comparator which uses natural order
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*/
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@SuppressWarnings("unchecked")
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public static <E extends Comparable<? super E>> Comparator<E> naturalComparator() {
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return NATURAL_COMPARATOR;
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}
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/**
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* Gets a comparator that compares using two {@link Comparator}s.
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* <p>
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* The second comparator is used if the first comparator returns equal.
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*
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* @param comparator1 the first comparator to use, not null
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* @param comparator2 the first comparator to use, not null
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* @return a {@link ComparatorChain} formed from the two comparators
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* @throws NullPointerException if either comparator is null
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* @see ComparatorChain
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*/
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@SuppressWarnings("unchecked")
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public static <E extends Comparable<? super E>> Comparator<E> chainedComparator(Comparator<E> comparator1, Comparator<E> comparator2) {
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return chainedComparator(new Comparator[] {comparator1, comparator2});
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}
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/**
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* Gets a comparator that compares using an array of {@link Comparator}s, applied
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* in sequence until one returns not equal or the array is exhausted.
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*
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* @param comparators the comparators to use, not null or empty or containing nulls
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* @return a {@link ComparatorChain} formed from the input comparators
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* @throws NullPointerException if comparators array is null or contains a null
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* @see ComparatorChain
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*/
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public static <E extends Comparable<? super E>> Comparator<E> chainedComparator(Comparator<E>[] comparators) {
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ComparatorChain<E> chain = new ComparatorChain<E>();
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for (int i = 0; i < comparators.length; i++) {
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if (comparators[i] == null) {
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throw new NullPointerException("Comparator cannot be null");
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}
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chain.addComparator(comparators[i]);
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}
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return chain;
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}
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/**
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* Gets a comparator that compares using a collection of {@link Comparator}s,
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* applied in (default iterator) sequence until one returns not equal or the
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* collection is exhausted.
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*
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* @param comparators the comparators to use, not null or empty or containing nulls
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* @return a {@link ComparatorChain} formed from the input comparators
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* @throws NullPointerException if comparators collection is null or contains a null
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* @throws ClassCastException if the comparators collection contains the wrong object type
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* @see ComparatorChain
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*/
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@SuppressWarnings("unchecked")
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public static <E extends Comparable<? super E>> Comparator<E> chainedComparator(Collection<Comparator<E>> comparators) {
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return chainedComparator(
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(Comparator<E>[]) comparators.toArray(new Comparator[comparators.size()])
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);
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}
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/**
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* Gets a comparator that reverses the order of the given comparator.
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*
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* @param comparator the comparator to reverse
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* @return a comparator that reverses the order of the input comparator
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* @see ReverseComparator
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*/
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public static <E> Comparator<E> reversedComparator(Comparator<E> comparator) {
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return new ReverseComparator<E>(comparator);
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}
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/**
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* Gets a Comparator that controls the comparison of <code>null</code> values.
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* <p>
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* The returned comparator will consider a null value to be less than
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* any nonnull value, and equal to any other null value. Two nonnull
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* values will be evaluated with the given comparator.
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*
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* @param comparator the comparator that wants to allow nulls
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* @return a version of that comparator that allows nulls
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* @see NullComparator
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*/
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@SuppressWarnings("unchecked")
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public static <E> Comparator<E> nullLowComparator(Comparator<E> comparator) {
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if (comparator == null) {
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comparator = NATURAL_COMPARATOR;
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}
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return new NullComparator<E>(comparator, false);
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}
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/**
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* Gets a Comparator that controls the comparison of <code>null</code> values.
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* <p>
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* The returned comparator will consider a null value to be greater than
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* any nonnull value, and equal to any other null value. Two nonnull
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* values will be evaluated with the given comparator.
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*
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* @param comparator the comparator that wants to allow nulls
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* @return a version of that comparator that allows nulls
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* @see NullComparator
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*/
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@SuppressWarnings("unchecked")
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public static <E> Comparator<E> nullHighComparator(Comparator<E> comparator) {
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if (comparator == null) {
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comparator = NATURAL_COMPARATOR;
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}
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return new NullComparator<E>(comparator, true);
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}
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/**
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* Returns the smaller of the given objects according to the given
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* comparator, returning the second object if the comparator
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* returns equal.
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*
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* @param o1 the first object to compare
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* @param o2 the second object to compare
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* @param comparator the sort order to use
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* @return the smaller of the two objects
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*/
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@SuppressWarnings("unchecked")
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public static <E> E min(E o1, E o2, Comparator<E> comparator) {
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if (comparator == null) {
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comparator = NATURAL_COMPARATOR;
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}
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int c = comparator.compare(o1, o2);
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return (c < 0) ? o1 : o2;
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}
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/**
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* Returns the larger of the given objects according to the given
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* comparator, returning the second object if the comparator
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* returns equal.
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*
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* @param o1 the first object to compare
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* @param o2 the second object to compare
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* @param comparator the sort order to use
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* @return the larger of the two objects
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*/
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@SuppressWarnings("unchecked")
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public static <E> E max(E o1, E o2, Comparator<E> comparator) {
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if (comparator == null) {
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comparator = NATURAL_COMPARATOR;
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}
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int c = comparator.compare(o1, o2);
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return (c > 0) ? o1 : o2;
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}
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}
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