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A common support library.

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/*
 * Copyright 2016 UsefulMilk
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.usefulmilk.support.domain;

/**
 * According to Eric Evans, Entity are objects that have a distinct identity
 * that runs through time and different representations. You also hear these
 * called "reference objects".
 * Two different instances of {@link Entity} are equals when the values
 * returned by {@link Entity#getId()} are equals.
 */
public abstract class Entity extends DomainObject {
    /**
     * It compares the {@link Entity#getId()} of parameter object with
     * this {@link Entity#getId()}. If are equals, it will return true.
     * @param obj Object to be compared.
     * @return Return true if the objects are equals.
     */
    @Override
    public boolean equals(Object obj) {
        if(obj instanceof Entity) {
            return idEquals(this, (Entity) obj);
        }

        return false;
    }

    /**
     * It will return the hashCode generated by {@link Entity#getId()}.
     * @return The hashCode of this object.
     */
    @Override
    public int hashCode() {
        return getIdHashCode(this);
    }
}