Returns the greatest integer double value no greater than this.
If this is already an integer valued double, including -0.0, or it is not
a finite value, the value is returned unmodified.
For the purpose of rounding, -0.0 is considered to be below 0.0.
A number d in the range 0.0 < d < 1.0 will return 0.0.
Source
/**
* Returns the greatest integer double value no greater than `this`.
*
* If this is already an integer valued double, including `-0.0`, or it is not
* a finite value, the value is returned unmodified.
*
* For the purpose of rounding, `-0.0` is considered to be below `0.0`.
* A number `d` in the range `0.0 < d < 1.0` will return `0.0`.
*/
double floorToDouble();