Java中的浮点数和double数据类型 [英] Float and double datatype in java
问题描述
这是什么意思?何时应该使用float而不是double,反之亦然。
总结: / p>
-
float
以32位表示,具有1个符号位,8指数的位和23位的有效位数(或从科学计数符号:2.33728 * 10 12 ; 33728是有效位数)。 -
double
以64位表示,具有1个符号位,11位指数和52位有效位数。
默认情况下,Java使用 double
表示其浮点数字(所以文字 3.14
键入 double
)。这也是数据类型,它会给你一个更大的数字范围,所以我强烈建议使用 float
。
可能有某些库实际上强制您使用 float
,但一般情况下,除非您能保证您的结果足够小以适应 float
的规定范围,那么最好选择使用 double
。
如果您需要准确性 - 例如,您不能具有不准确的十进制值(例如 1/10 + 2/10
),或者您正在执行任何任何货币(例如,在系统中代表10.33美元),然后使用一个 BigDecimal
,它可以支持任意数量的精度,并处理优雅的情况。
The float data type is a single-precision 32-bit IEEE 754 floating point and The double data type is a double-precision 64-bit IEEE 754 floating point.
What does it mean? And when should I use float instead of double or vice-versa.
The Wikipedia page on it is a good place to start.
To sum up:
float
is represented in 32 bits, with 1 sign bit, 8 bits of exponent, and 23 bits of the significand (or what follows from a scientific-notation number: 2.33728*1012; 33728 is the significand).double
is represented in 64 bits, with 1 sign bit, 11 bits of exponent, and 52 bits of significand.
By default, Java uses double
to represent its floating-point numerals (so a literal 3.14
is typed double
). It's also the data type that will give you a much larger number range, so I would strongly encourage its use over float
.
There may be certain libraries that actually force your usage of float
, but in general - unless you can guarantee that your result will be small enough to fit in float
's prescribed range, then it's best to opt with double
.
If you require accuracy - for instance, you can't have a decimal value that is inaccurate (like 1/10 + 2/10
), or you're doing anything with currency (for example, representing $10.33 in the system), then use a BigDecimal
, which can support an arbitrary amount of precision and handle situations like that elegantly.
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