Returns the double integer value obtained by discarding any fractional
digits from the double value of this.
If this is already an integer valued double, including -0.0, or it is a
non-finite double 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 -1.0 < d < 0.0 will return -0.0, and
in the range 0.0 < d < 1.0 it will return 0.0.
The result is always a double. If this is a numerically large integer, the result may be an infinite double.
Source
double truncateToDouble();