Answer:
// program in java.
// package
import java.util.*;
// class definition
class Main
{
// main method of the class
public static void main (String[] args) throws java.lang.Exception
{
try{
// Scanner object to read input
Scanner scr=new Scanner(System.in);
// variables
double rad;
String unit1="in";
String unit2="ft";
String unit3="cm";
String unit4="m";
// ask user to enter radius
System.out.print("Enter the radius: ");
// read radius
rad=scr.nextDouble();
// check radius is negative or not
while(rad<0)
{
System.out.println("Radius can't be negative:");
// ask again to enter radius
System.out.print("Enter the Radius again:");
// read radius again
rad=scr.nextInt();
}
// ask user to enter the unit of measurement
System.out.print("Enter the unit (\"in\" for inch, \"ft\" for feet, \"cm\" for centimeter, and \"m\" for meter):");
// read unit
String unt=scr.next();
// calculate area
double area=3.14*rad*rad;
// print area and unit
if(unt.equals(unit1))
System.out.println(area+" inch.");
else if(unt.equals(unit2))
System.out.println(area+" feet.");
else if(unt.equals(unit3))
System.out.println(area+" centimeter.");
else if(unt.equals(unit4))
System.out.println(area+" meter.");
}catch(Exception ex){
return;}
}
}
Explanation:
Read radius of circle from user with Scanner object and assign it to variable "rad".Check the radius is negative or not.If the radius is negative ask user to enter radius again until user enters a positive radius.Then read the unit of measurement.calculate the area of circle and print area with unit.
Output:
Enter the radius: -4
Radius can't be negative:
Enter the Radius again:6
Enter the unit ("in" for inch, "ft" for feet, "cm" for centimeter, and "m" for meter):cm
Area of circle is 113.03999999999999 centimeter.
