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