    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}