Besides the types for representing integer numbers, in Java there are two primitive data types for representing real numbers. Due to the way in which real numbers are represented internally in memory, these numbers are also called floating point numbers.
The data type for floating point numbers that is used by default in the Java mathematical library is double.
| Type | double | ||
| Dimension | 64 bit (8 byte) | ||
| Domain | set of 264 positive and | Minimum absolute value | 1.79769313486231570 . 10-308 |
| negative real numbers | Maximum absolute value | 2.250738585072014 . 10+308 | |
| Precision |  15 decimal digits |
||
| Operations | + | sum | |
| - | difference | ||
| * | product | ||
| / | division | ||
| Literals | sequences of digits with decimal dot optionally ending with a d (or D) | ||
| denoting values of the domain (e.g., 3.14 or 3.14d) | |||
| representation in scientific notation (e.g., 314E-2 or 314E-2d) | |||
Example:
double pi, p2; // Declaration of variables of type double pi = 3.14; // Use of literals p2 = 628E-2d; // Use of literals p2 = pi * 2; // Arithmetic expression