The double data type uses 64 bits to store a floating-point number. double value is also known as a double-precision floating-point number.
It can represent a number as small as 4.9 x 10-324 and as big as 1.7 x 10308 in magnitude.
It could be positive or negative.
All real numbers are called double literals. A double literal may optionally end with d or D, for example, 1.27d.
The suffix d or D is optional in double literals.
Both 19.7 and 19.7d represent the same double literal.
A double literal can be expressed in the following two formats:
Examples of double literals in decimal number format are as follows:
double d1 = 8D ; double d2 = 8.; double d3 = 8.0; double d4 = 8.D; double d5 = 78.9867; double d6 = 45.0;
8 is an int literal whereas 8D, 8., and 8.0 are double literals.
We can also use scientific notation to express double literals.
double d1 = 32.5E-1; double d2 = 0.325E+1; double d3 = 0.325E1; double d4 = 0.0325E2; double d5 = 0.0325e2; double d6 = 32.5E-1D; double d7 = 0.325E+1d; double d8 = 0.325E1d; double d9 = 0.0325E2d;
The double data type defines two zeros, two infinities, and a NaN. They are represented by constants in the Double class.
The following table lists these constants and their meanings.
| Constants | Meaning |
|---|---|
| Double.POSITIVE_INFINITY | Positive infinity of type double |
| Double.NEGATIVE_INFINITY | Negative infinity of type double |
| Double.NaN | Not a Number of type double |
| Double.MAX_VALUE | The largest positive value that can be represented in a double variable. This is equal to 1.7 x 10308 |
| Double.MIN_VALUE | The smallest positive value greater than zero that can be represented in a double variable. This is equal to 4.9 x 10-324. |
The value of all integral types (int, long, byte, short, char) and float can be assigned to a variable of the double data type without using an explicit cast.
int num1 = 15;
double salary = num1;
salary = 12345;
double bigNum = Double.MAX_VALUE;
bigNum = 1234L;
double justAChar = 'A';
double dInf = Double.POSITIVE_INFINITY;
double dNan = Double.NaN;
A double value must be cast to the integral type before it is assigned to a variable of any integral data type (int, long, byte, short, or char).