Floating-point numbers are like real numbers in mathematics,
for example, 3.14159, -0.000001. Java has two kinds of floating-point
numbers: float
and
double
, both stored in IEEE-754 format.
The default type when you write a floating-point literal is double
.
type | Size | Range | Precision | |
name | bytes | bits | approximate | in decimal digits |
float | 4 | 32 | +/- 3.4 * 1038 | 6-7 |
double | 8 | 64 | +/- 1.8 * 10308 | 15 |
Because there are only a limited number of bits in each floating-point type, some numbers are inexact, just as the decimal system can not represent some numbers exactly, for example 1/3. The most troublesome of these is that 1/10 can not be represented exactly in binary.
There are two types of notation for floating-point numbers. Any of these numbers
can be followed by "F" (or "f") to make it a float
instead of the
default double
.
double
. A sign (+ or -) may precede the number.Scientific | Standard |
---|---|
1.2345e5 | 123450.0 |
1.2345e+5 | 123450.0 |
1.2345e-5 | 0.000012345 |
No exceptions are generated by floating-point operations. Instead of an interruption in execution, the result of an operation may be positive infinity, negative infinity, or NaN (not a number). Division by zero or overflow produce infinity. Subtracting two infinities produces a NaN. Use methods in the wrapper classes (Float or Double) to test for these values.