org.springframework.util.comparator.InvertibleComparator.java Source code

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Here is the source code for org.springframework.util.comparator.InvertibleComparator.java

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/*
 * Copyright 2002-2018 the original author or authors.
 *
 * 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
 *
 *      https://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.springframework.util.comparator;

import java.io.Serializable;
import java.util.Comparator;

import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

/**
 * A decorator for a comparator, with an "ascending" flag denoting
 * whether comparison results should be treated in forward (standard
 * ascending) order or flipped for reverse (descending) order.
 *
 * @author Keith Donald
 * @author Juergen Hoeller
 * @since 1.2.2
 * @param <T> the type of objects that may be compared by this comparator
 * @deprecated as of Spring Framework 5.0, in favor of the standard JDK 8
 * {@link Comparator#reversed()}
 */
@Deprecated
@SuppressWarnings("serial")
public class InvertibleComparator<T> implements Comparator<T>, Serializable {

    private final Comparator<T> comparator;

    private boolean ascending = true;

    /**
     * Create an InvertibleComparator that sorts ascending by default.
     * For the actual comparison, the specified Comparator will be used.
     * @param comparator the comparator to decorate
     */
    public InvertibleComparator(Comparator<T> comparator) {
        Assert.notNull(comparator, "Comparator must not be null");
        this.comparator = comparator;
    }

    /**
     * Create an InvertibleComparator that sorts based on the provided order.
     * For the actual comparison, the specified Comparator will be used.
     * @param comparator the comparator to decorate
     * @param ascending the sort order: ascending (true) or descending (false)
     */
    public InvertibleComparator(Comparator<T> comparator, boolean ascending) {
        Assert.notNull(comparator, "Comparator must not be null");
        this.comparator = comparator;
        setAscending(ascending);
    }

    /**
     * Specify the sort order: ascending (true) or descending (false).
     */
    public void setAscending(boolean ascending) {
        this.ascending = ascending;
    }

    /**
     * Return the sort order: ascending (true) or descending (false).
     */
    public boolean isAscending() {
        return this.ascending;
    }

    /**
     * Invert the sort order: ascending -> descending or
     * descending -> ascending.
     */
    public void invertOrder() {
        this.ascending = !this.ascending;
    }

    @Override
    public int compare(T o1, T o2) {
        int result = this.comparator.compare(o1, o2);
        if (result != 0) {
            // Invert the order if it is a reverse sort.
            if (!this.ascending) {
                if (Integer.MIN_VALUE == result) {
                    result = Integer.MAX_VALUE;
                } else {
                    result *= -1;
                }
            }
            return result;
        }
        return 0;
    }

    @Override
    @SuppressWarnings("unchecked")
    public boolean equals(@Nullable Object other) {
        if (this == other) {
            return true;
        }
        if (!(other instanceof InvertibleComparator)) {
            return false;
        }
        InvertibleComparator<T> otherComp = (InvertibleComparator<T>) other;
        return (this.comparator.equals(otherComp.comparator) && this.ascending == otherComp.ascending);
    }

    @Override
    public int hashCode() {
        return this.comparator.hashCode();
    }

    @Override
    public String toString() {
        return "InvertibleComparator: [" + this.comparator + "]; ascending=" + this.ascending;
    }

}