Float and double datatype in Java

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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