程序编译时没有错误但不会执行..出了什么问题？

Question

import java.io.*;
import java.util.*;
public class popGrowth
{

    public static void main (String args[])
    {

        Scanner keyboard = new Scanner(System.in);
        double rate = keyboard.nextDouble();
            while (rate != 0.0){ //stops it at zero


            double initialPop = 236; //in millions
                for (int i = 0; i < 20; i++)// i establishes the year
                {
                    int year = i + 2010;// starts the year at 2010
                    double population = initialPop * Math.pow(1+rate/(double)(12*100), (12*i)); //finds population
                    System.out.println("Year: /tPopulation in millions"); 
                    System.out.println(year + "/t " + population); //prints year

            }


            double timeToDouble = 72/rate; //rule of 72
            System.out.println("Time to double " + timeToDouble);
            System.out.print("Please input new rate "); 
            rate = keyboard.nextDouble(); //input for zero

        } 

    }
   }

这是我的确切代码，我不知道为什么它会在没有错误的情况下编译就无法运行。