Higher Interest

We obviously need to find a bank with an interest rate higher than five percent. Say that you are willing to wait 40 years for your million dollars. How high must the interest rate be?

One way to answer this question is to try out various interest rates until you find one that works. Here is a program that does that:

import java.util.Scanner;

class DollarsAfterForty
{

  public static void main( String[] args ) 
  {
    double dollars = 1000.00 ;
    double rate;
    int    year =  1 ;     

    // get the interest rate from the user
    Scanner scan = new Scanner( System.in );
    System.out.print("Enter the interest rate in percent: "); 
    rate = scan.nextDouble()/100.0 ;
 
    while (  year <=  )
    {
      // add another year's interest
      dollars =  dollars + dollars *  ; 

      // add in this year's contribution
      dollars = dollars + 1000 ;

      year    =  year + 1 ;
    }

    System.out.println("After 40 years at " + rate*100 
      + " percent interest you will have " + dollars + " dollars" );
  }

}

This program does NOT use a result-controlled loop. It uses a counting loop because the counter, year, is used to control the loop.