The double keyword is used to declare a primitive Java data type containing a 64-bit floating-point number in IEEE 754 format. Variables of type double store values in the range negative 1.7E308 to positive 1.7E308 within approximately 14 significant digits of accuracy. When you want a floating-point literal value to be treated as a double, append the letters 'd' or 'D' to the end of the value.
Note that double variables may be cast to and from other numeric types. However, doubles cannot be cast to or from values of type boolean.
The following example demonstrates declaration and assignment for a double variable:
private double dCalcSet;
dCalcSet = 1.23d;
dCalcSet = 3e2;
dCalcSet = .25;