    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017
    018package org.apache.commons.lang3.compare;
    019
    020import java.io.Serializable;
    021import java.util.Comparator;
    022
    023/**
    024 * Compares Object's {@link Object#toString()} values.
    025 *
    026 * This class is stateless.
    027 *
    028 * @since 3.10
    029 */
    030public final class ObjectToStringComparator implements Comparator<Object>, Serializable {
    031
    032    /**
    033     * Singleton instance.
    034     *
    035     * This class is stateless.
    036     */
    037    public static final ObjectToStringComparator INSTANCE = new ObjectToStringComparator();
    038
    039    /**
    040     * For {@link Serializable}.
    041     */
    042    private static final long serialVersionUID = 1L;
    043
    044    @Override
    045    public int compare(final Object o1, final Object o2) {
    046        if (o1 == null && o2 == null) {
    047            return 0;
    048        }
    049        if (o1 == null) {
    050            return 1;
    051        }
    052        if (o2 == null) {
    053            return -1;
    054        }
    055        final String string1 = o1.toString();
    056        final String string2 = o2.toString();
    057        // No guarantee that toString() returns a non-null value, despite what Spotbugs thinks.
    058        if (string1 == null && string2 == null) {
    059            return 0;
    060        }
    061        if (string1 == null) {
    062            return 1;
    063        }
    064        if (string2 == null) {
    065            return -1;
    066        }
    067        return string1.compareTo(string2);
    068    }
    069}