    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    /**
    045     * Constructs a new instance.
    046     *
    047     * @deprecated Will be private in 4.0.0.
    048     */
    049    @Deprecated
    050    public ObjectToStringComparator() {
    051        // empty
    052    }
    053
    054    @Override
    055    public int compare(final Object o1, final Object o2) {
    056        if (o1 == null && o2 == null) {
    057            return 0;
    058        }
    059        if (o1 == null) {
    060            return 1;
    061        }
    062        if (o2 == null) {
    063            return -1;
    064        }
    065        final String string1 = o1.toString();
    066        final String string2 = o2.toString();
    067        // No guarantee that toString() returns a non-null value, despite what Spotbugs thinks.
    068        if (string1 == null && string2 == null) {
    069            return 0;
    070        }
    071        if (string1 == null) {
    072            return 1;
    073        }
    074        if (string2 == null) {
    075            return -1;
    076        }
    077        return string1.compareTo(string2);
    078    }
    079}