問題描述

float 數據類型是單精度 32 位 IEEE 754 浮點數，double 數據類型是雙精度 64 位 IEEE 754 浮點數.

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?我什么時候應該使用 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很好的起點.

總結一下:

• float 用 32 位表示，有 1 個符號位、8 位指數和 23 位有效數字(或從科學記數法數得出的數字:2.33728*10¹²；33728 是有效位).

• 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 用 64 位表示，有 1 個符號位、11 位指數和 52 位有效位.

double is represented in 64 bits, with 1 sign bit, 11 bits of exponent, and 52 bits of significand.

默認情況下，Java 使用 double 來表示它的浮點數(所以文字 3.14 的類型是 double).它也是可以為您提供更大數字范圍的數據類型，因此我強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.

可能有某些庫實際上會強制您使用 float，但總的來說 - 除非您可以保證您的結果足夠小以適合 float's 規定范圍，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.

如果您需要準確性 - 例如，您不能有不準確的十進制值(例如 1/10 + 2/10)，或者您正在做任何事情 與貨幣(例如，在系統中表示 $10.33)，然后使用 BigDecimal，它可以支持任意數量的精度并優雅地處理此類情況.

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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