how to write this java program

题目

how to write this java program
the question is:The height of an object dropped from a starting height of 100 meters is govern by the equation h=100-4.9*t^2 where t is the time in seconds.Write a program that asks the user for a time less than 20 seconds and displays the height of the object at that time using this formula.The output should look similar to:
Enter the time:2
The object is at 80.4 meter
im in usa·this is my computer homework·i cannot type in Chinese·sorry

答案

hi,here is my program.
it is my pleasure to help u!
import java.util.Scanner;
public class App {
/**
* @param args
*/
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
int time = 0;
do {
System.out.println("Please input a time less than 20 seconds!");
time = s.nextInt();
} while (time >= 20 || time < 0);
System.out.println("The object is at " + (100 - 4.9 * time * time)
+ " meter!");
}
}