Question

Assume that the population of Mexico is 128 million and that the population increases 1.01 percent annually. Assume that the population of the United States is 323 million and that the population is reduced 0.15 percent annually. Write an application that displays the populations for the two countries every year until the population of Mexico exceeds that of the United States, and display the number of years it took. Save the file as Population.java.

Answer 1

Population.java file:

public class Population {
  
   private static double Mexico = 128.0; // initial population of Mexico in million
   private static double Mexico_growth_rate = 1.01; // population increase by this rate every year
   private static double UnitedStates = 323.0; // initial population of United States in million
   private static double US_growth_rate = -0.15; // negative growth rate as population decrease by this rate each year
   private static int count = 0; // variable to hold number of years taken
  
   //main method to run the program
   public static void main(String args[]) {
       // print header for output
       String s = String.format("%s %12s %22s", "Year", "Mexico", "United States"); // formating string for output
       System.out.println(s);
       while(true) {
           // print out the population for current year
           print(count, Mexico, UnitedStates);
           // check if population of Mexico exceeds that of the United States
           if(Mexico > UnitedStates) {
               // break the loop as condition for program ending are met
               break;
           }
           else {
               // calculate Mexico's population
               Mexico = Mexico + (Mexico*Mexico_growth_rate/100.0);
               // calculate United States's population
               UnitedStates = UnitedStates + (UnitedStates*US_growth_rate/100.0);
               // increase count by 1
               count++;
           }
       }//end of while loop
       // print result message
       System.out.println();
       System.out.print("It takes ");
       System.out.print(count);
       System.out.println(" years for population of Mexico to exceed that of the United States");
   }

   private static void print(int year, double mexico, double unitedStates) {
       // formating string for output
       String str = String.format("%2d %10.2f %s %10.2f %s", year, mexico, "million", unitedStates, "million");
       // print populations
       System.out.println(str);  
   }

}