問題描述
float 數(shù)據(jù)類型是單精度 32 位 IEEE 754 浮點(diǎn)數(shù)，double 數(shù)據(jù)類型是雙精度 64 位 IEEE 754 浮點(diǎn)數(shù).
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.
這是什么意思?我什么時(shí)候應(yīng)該使用 float 而不是 double 或反之亦然?
What does it mean? And when should I use float instead of double or vice-versa?
推薦答案
維基百科頁面這是一個(gè)很好的起點(diǎn).
總結(jié)一下:
float用 32 位表示，有 1 個(gè)符號(hào)位、8 位指數(shù)和 23 位有效數(shù)字(或從科學(xué)記數(shù)法數(shù)得出的數(shù)字:2.33728*1012；33728 是有效位).
floatis 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 用 64 位表示，有 1 個(gè)符號(hào)位、11 位指數(shù)和 52 位有效位.
double is represented in 64 bits, with 1 sign bit, 11 bits of exponent, and 52 bits of significand.
默認(rèn)情況下，Java 使用 double 來表示它的浮點(diǎn)數(shù)(所以文字 3.14 的類型是 double).它也是可以為您提供更大數(shù)字范圍的數(shù)據(jù)類型，因此我強(qiáng)烈建議使用它而不是 float.
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.
可能有某些庫實(shí)際上會(huì)強(qiáng)制您使用 float，但總的來說 - 除非您可以保證您的結(jié)果足夠小以適合 float's 規(guī)定范圍，那么最好選擇與 double.
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.
如果您需要準(zhǔn)確性 - 例如，您不能有不準(zhǔn)確的十進(jìn)制值(例如 1/10 + 2/10)，或者您正在做任何事情 與貨幣(例如，在系統(tǒng)中表示 $10.33)，然后使用 BigDecimal，它可以支持任意數(shù)量的精度并優(yōu)雅地處理此類情況.
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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