阅读jdk1.8源码小收获

分享一个阅读源码中收获的小的优化方案。

在创建一个Boolean时，Boolean b = true;不是一个好的方案，在源码中有一个更好的 建议，可以节省时间和空间

Boolean bool = Boolean.valueOf(true);
这个是jdk源码推荐的方法

源码和注释如下：

/** * Returns a {@code Boolean} instance representing the specified * {@code boolean} value.  If the specified {@code boolean} value * is {@code true}, this method returns {@code Boolean.TRUE}; * if it is {@code false}, this method returns {@code Boolean.FALSE}. * If a new {@code Boolean} instance is not required, this method * should generally be used in preference to the constructor * {@link #Boolean(boolean)}, as this method is likely to yield * significantly better space and time performance. * * @param  b a boolean value. * @return a {@code Boolean} instance representing {@code b}. * @since  1.4 */public static Boolean valueOf(boolean b) {    return (b ? TRUE : FALSE);}

阅读了Integer的源码 valueOf也是取的缓存中的值。

/** * Returns an {@code Integer} instance representing the specified * {@code int} value.  If a new {@code Integer} instance is not * required, this method should generally be used in preference to * the constructor {@link #Integer(int)}, as this method is likely * to yield significantly better space and time performance by * caching frequently requested values. * * This method will always cache values in the range -128 to 127, * inclusive, and may cache other values outside of this range. * * @param  i an {@code int} value. * @return an {@code Integer} instance representing {@code i}. * @since  1.5 */public static Integer valueOf(int i) {    if (i >= IntegerCache.low && i <= IntegerCache.high)        return IntegerCache.cache[i + (-IntegerCache.low)];    return new Integer(i);}

注意：Integer a = 3;这种情况默认走 valueOf() !!! Boolean b = true;也是默认走valueOf()方法！！

Integer c2 = new Integer(1);      官方不推荐这种建对象的方法喔