深入理解Java原始数据类型和包装类关于==和equals的比较

1.运算符 ==

对于六大Java数值类原始数据类型，==比较的是数值

对于六大Java原始数据类型对应的包装类，==比较的是内存地址

2.equals()

equals()方法只有对象才有，所以我们讨论一下原始数值类型的包装在的equals（）方法吧！

对于六大Java原始数据类型对应的包装类，equals都是比较值。

有源码为证如下所示：

Byte类

Short类

Integer类

Long类

Double类

/**     * Compares this object against the specified object.  The result     * is {@code true} if and only if the argument is not     * {@code null} and is a {@code Double} object that     * represents a {@code double} that has the same value as the     * {@code double} represented by this object. For this     * purpose, two {@code double} values are considered to be     * the same if and only if the method {@link     * #doubleToLongBits(double)} returns the identical     * {@code long} value when applied to each.     *     * <p>Note that in most cases, for two instances of class     * {@code Double}, {@code d1} and {@code d2}, the     * value of {@code d1.equals(d2)} is {@code true} if and     * only if     *     * <blockquote>     *  {@code d1.doubleValue() == d2.doubleValue()}     * </blockquote>     *     * <p>also has the value {@code true}. However, there are two     * exceptions:     * <ul>     * <li>If {@code d1} and {@code d2} both represent     *     {@code Double.NaN}, then the {@code equals} method     *     returns {@code true}, even though     *     {@code Double.NaN==Double.NaN} has the value     *     {@code false}.     * <li>If {@code d1} represents {@code +0.0} while     *     {@code d2} represents {@code -0.0}, or vice versa,     *     the {@code equal} test has the value {@code false},     *     even though {@code +0.0==-0.0} has the value {@code true}.     * </ul>     * This definition allows hash tables to operate properly.     * @param   obj   the object to compare with.     * @return  {@code true} if the objects are the same;     *          {@code false} otherwise.     * @see java.lang.Double#doubleToLongBits(double)     */    public boolean equals(Object obj) {        return (obj instanceof Double)               && (doubleToLongBits(((Double)obj).value) ==                      doubleToLongBits(value));    }

Float类

 /**     * Compares this object against the specified object.  The result     * is {@code true} if and only if the argument is not     * {@code null} and is a {@code Float} object that     * represents a {@code float} with the same value as the     * {@code float} represented by this object. For this     * purpose, two {@code float} values are considered to be the     * same if and only if the method {@link #floatToIntBits(float)}     * returns the identical {@code int} value when applied to     * each.     *     * <p>Note that in most cases, for two instances of class     * {@code Float}, {@code f1} and {@code f2}, the value     * of {@code f1.equals(f2)} is {@code true} if and only if     *     * <blockquote><pre>     *   f1.floatValue() == f2.floatValue()     * </pre></blockquote>     *     * <p>also has the value {@code true}. However, there are two exceptions:     * <ul>     * <li>If {@code f1} and {@code f2} both represent     *     {@code Float.NaN}, then the {@code equals} method returns     *     {@code true}, even though {@code Float.NaN==Float.NaN}     *     has the value {@code false}.     * <li>If {@code f1} represents {@code +0.0f} while     *     {@code f2} represents {@code -0.0f}, or vice     *     versa, the {@code equal} test has the value     *     {@code false}, even though {@code 0.0f==-0.0f}     *     has the value {@code true}.     * </ul>     *     * This definition allows hash tables to operate properly.     *     * @param obj the object to be compared     * @return  {@code true} if the objects are the same;     *          {@code false} otherwise.     * @see java.lang.Float#floatToIntBits(float)     */    public boolean equals(Object obj) {        return (obj instanceof Float)               && (floatToIntBits(((Float)obj).value) == floatToIntBits(value));    }