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