Complete the constructors and the sectorArea method of the Circle class.
public class Circle
{
private double radius;
// constructors
// postcondition: the instance variable is initialized
public Circle(double rad)
{
}
// postcondition: the instance variable is initialized
public Circle(int diameter)
{
}
// postcondition: returns the sector area of a circle with radius equal to
// this circle's radius, according to the formula: (deg / 360) * PI * r^2,
// where deg is the angle in degrees passed as the parameter,
// PI is the value of pi (3.1415...), r is the radius of the circle,
// and "^2" means raised to the second power.
// Use the Math class constant to represent the value of pi.
public double sectorArea(double degree)
{
}
// There may be other instance variables, constructors,
// and methods that are not shown.
}