Question

Write a program that will predict the size of a population of organisms. The program should ask for the starting number of organisms, their average daily population increase (as a percentage), and the number of days they will multiply.
For example, a population might begin with two organisms, have an average daily increase of 50 percent, and will be allowed to multiply for seven days. The program should use a loop to display the size of the population for each day.
Input Validation:
 Do not accept a number less than 2 for the starting size of the population.
 Do not accept a negative number for average daily population increase.
 Do not accept a number less than 1 for the number of days they will multiply.
 Your program must a recursive method instead of a loop to calculate the number of organisms.

Here's the code. The code runs however the daily increase is wrong. When i plug in the number of oganisms to be 15 , daily incease to be 30 and the days to be 7, it should print out 1    15.0, 2 19.5, 3 25.35, 4 32.955, 5 42.842, 6 55.694 and 7 72.402. Thanks for your help

import java.util.Scanner;
import java.text.DecimalFormat;
public class Population
{
   private double showPopulation(int dayNum, int days,double organisms,double dailyIncrease) //private function each day population display
   {
       if (dayNum == days)
        return organisms;
       else
       return (organisms*(dailyIncrease)/100); //caculate population %
   }
    
   public void displayPopulation(double startingOrgnisms,double increase,int days)
   {
       DecimalFormat formatter = new DecimalFormat("###,###,###,###,###.000000000000");
       double dailyIncrease=startingOrgnisms;
       System.out.println("Days            Organisms");
       System.out.println("----------------------------------");
     
       for(int i=1;i <= days;i++) //repeating loop fo no.of days
       {
       dailyIncrease+=showPopulation(i,days,startingOrgnisms,increase); //calling private function to display each population
       System.out.println(i+"                 "+formatter.format(dailyIncrease)); //printing the output
   }
   }
   public static void main(String args[])
   {
       double startingOrgnisms,increase;
       int days;
       Population p1=new Population(); //create object of Population
    
       Scanner s=new Scanner(System.in); //create Scanner object for reading
       while(true) //repeat loop,if population size entered is <2
       {
       System.out.println("Enter the starting number of organisms: ");
       startingOrgnisms=s.nextDouble(); //input population
       if(startingOrgnisms>=2) break;//if valid input exit loop
       System.out.println("Invalid! enter more than 2 for population"); //otherwise error message and repeat loop
       }
    
       while(true) //repeat loop, if average increase <0
       {
       System.out.println("Enter the daily Increase : ");
       increase=s.nextDouble(); //input increase average value
       if(increase>0) break; //if input is valid then exit loop
       System.out.println("Invalid! enter greater than 0 for daily increase"); //otherwise error message and repeat loop
       }
    
       while(true) //loop for validating no.of days
       {
       System.out.println("Enter the number of days organisms will multiply : ");
       days=s.nextInt();//input days
       if(days>0) break; //if right input exit loop
       System.out.println("Please! enter greater than 0 for the number of days organisms will multiply ");
        //otherwise error and repeat the loop
       }
    
       p1.displayPopulation(startingOrgnisms,increase,days); //calling function to display all
    
   }
}

Answer 1

import java.util.Scanner;
import java.text.DecimalFormat;
public class Population
{
private double showPopulation(int dayNum, int days,double organisms,double dailyIncrease) //private function each day population display
{
if (dayNum == days)
return organisms;
else
return (organisms*(dailyIncrease)/100); //caculate population %
}
  
public void displayPopulation(double startingOrgnisms,double increase,int days)
{
DecimalFormat formatter = new DecimalFormat("###,###,###,###,###.000000000000");
double dailyIncrease=startingOrgnisms;
System.out.println("Days Organisms");
System.out.println("----------------------------------");

for(int i=1;i <= days;i++) //repeating loop fo no.of days
{   
dailyIncrease+=showPopulation(i,days,startingOrgnisms,increase); //calling private function to display each population
startingOrganisms = dailyIncrease;
System.out.println(i+" "+formatter.format(dailyIncrease)); //printing the output
}
}
public static void main(String args[])
{
double startingOrgnisms,increase;
int days;
Population p1=new Population(); //create object of Population
  
Scanner s=new Scanner(System.in); //create Scanner object for reading
while(true) //repeat loop,if population size entered is <2
{
System.out.println("Enter the starting number of organisms: ");
startingOrgnisms=s.nextDouble(); //input population
if(startingOrgnisms>=2) break;//if valid input exit loop
System.out.println("Invalid! enter more than 2 for population"); //otherwise error message and repeat loop
}
  
while(true) //repeat loop, if average increase <0
{
System.out.println("Enter the daily Increase : ");
increase=s.nextDouble(); //input increase average value
if(increase>0) break; //if input is valid then exit loop
System.out.println("Invalid! enter greater than 0 for daily increase"); //otherwise error message and repeat loop
}
  
while(true) //loop for validating no.of days
{
System.out.println("Enter the number of days organisms will multiply : ");
days=s.nextInt();//input days
if(days>0) break; //if right input exit loop
System.out.println("Please! enter greater than 0 for the number of days organisms will multiply ");
//otherwise error and repeat the loop
}
  
p1.displayPopulation(startingOrgnisms,increase,days); //calling function to display all
  
}
}