Answer 1

You can ask the user for a number in that range, check the input, and loop if it isn't in the right range.

http://code.sololearn.com/cRT2zVdWYuBW

import java.util.Scanner;

public class Program
{
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
Double d = -1.0;
while ((d < 0.0) || (d > 100.0)) {
System.out.println("Please enter a number between 0 and 100.");
d = Double.parseDouble(sc.nextLine());
if ((d < 0.0) || (d > 100.0)) {
System.out.println("Value out of range!");
}
}
System.out.println(d);
}
}

while