Im attempting to write a program that takes a population's birthrate and deathrate and loops the annual population until it either reaches 0 or doubles. My problem it that it continuously loops an endless amount of illegible numbers and i cant fix it. please help.

//*****************************************
//This program displays loop statements
//Written by: Daniel Kellogg
//Last Edited: 9/28/12
//****************************************

import java.util.Scanner;
public class Hwk6 {
        public static void main (String[] args) {
                int currentYear, currentPopulation;
                double birthRate, deathRate;
                Scanner stdin = new Scanner(System.in);

                System.out.println("\nPopulation Estimator\n");
                System.out.println("Enter Year");
                currentYear = stdin.nextInt();
                System.out.println("Enter Current Population");
                currentPopulation = stdin.nextInt();
                System.out.println("Enter Birthrate of Population");
                birthRate = stdin.nextDouble();
                System.out.println("Enter Deathrate of Population");
                deathRate = stdin.nextDouble();

                int counter = currentPopulation;
                System.out.println("Population: ");
                while (currentPopulation != -1)
                while (counter < currentPopulation * 2) {
                        System.out.print(counter + " ");
                        counter = counter + (int)(counter * birthRate - counter * deathRate);
                }
                System.exit(0);
        }
}