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 *      https://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.mutable;
019
020import java.io.Serializable;
021import java.util.Objects;
022import java.util.concurrent.atomic.AtomicReference;
023
024/**
025 * A mutable {@link Object} wrapper.
026 * <p>
027 * This class was created before the introduction of {@link AtomicReference}.
028 * </p>
029 *
030 * @param <T> the type to set and get.
031 * @see AtomicReference
032 * @since 2.1
033 */
034public class MutableObject<T> implements Mutable<T>, Serializable {
035
036    /**
037     * Required for serialization support.
038     *
039     * @see java.io.Serializable
040     */
041    private static final long serialVersionUID = 86241875189L;
042
043    /** The mutable value. */
044    private T value;
045
046    /**
047     * Constructs a new MutableObject with the default value of {@code null}.
048     */
049    public MutableObject() {
050    }
051
052    /**
053     * Constructs a new MutableObject with the specified value.
054     *
055     * @param value  the initial value to store.
056     */
057    public MutableObject(final T value) {
058        this.value = value;
059    }
060
061    /**
062     * Compares this object against the specified object. The result is {@code true} if and only if the argument
063     * is not {@code null} and is a {@link MutableObject} object that contains the same {@link T}
064     * value as this object.
065     *
066     * @param obj  the object to compare with, {@code null} returns {@code false}.
067     * @return  {@code true} if the objects are the same;
068     *          {@code true} if the objects have equivalent {@code value} fields;
069     *          {@code false} otherwise.
070     */
071    @Override
072    public boolean equals(final Object obj) {
073        if (obj == null) {
074            return false;
075        }
076        if (this == obj) {
077            return true;
078        }
079        if (this.getClass() == obj.getClass()) {
080            final MutableObject<?> that = (MutableObject<?>) obj;
081            return Objects.equals(this.value, that.value);
082        }
083        return false;
084    }
085
086    /**
087     * Gets the value.
088     *
089     * @return the value, may be null.
090     */
091    @Override
092    public T getValue() {
093        return this.value;
094    }
095
096    /**
097     * Returns the value's hash code or {@code 0} if the value is {@code null}.
098     *
099     * @return the value's hash code or {@code 0} if the value is {@code null}.
100     */
101    @Override
102    public int hashCode() {
103        return Objects.hashCode(value);
104    }
105
106    /**
107     * Sets the value.
108     *
109     * @param value  the value to set.
110     */
111    @Override
112    public void setValue(final T value) {
113        this.value = value;
114    }
115
116    /**
117     * Returns the String value of this mutable.
118     *
119     * @return the mutable value as a string.
120     */
121    @Override
122    public String toString() {
123        return Objects.toString(value);
124    }
125
126}