ProportionalCountries.java

package com.jadekler.app;

import java.util.Random;

/**
 * Hello world!
 *
 */
public class ProportionalCountries 
{
    public String[] countryNames = {"USA", "China", "Vatican", "SA"};
    public int[] countryPops = {31300, 1351000000, 798, 511900000};
    public int[] popProportionalBuckets;
    public int popSum;

    public static void main( String[] args )
    {
        ProportionalCountries pc = new ProportionalCountries();
        
        for (int i = 0; i < 10; i++) {
            String country = pc.getRandomCountry();
            
            System.out.println(country);
        }
    }

    public ProportionalCountries() {
        int popSum = 0;

        for (int i = 0; i < this.countryPops.length; i++) {
            popSum += this.countryPops[i];
        }

        this.popSum = popSum;

        this.popProportionalBuckets = new int[this.countryPops.length];

        for (int i = 0; i < this.popProportionalBuckets.length; i++) {
            int proportion = (int)((1.0*this.countryPops[i]/popSum)*100);
            this.popProportionalBuckets[i] = proportion;
        }
    }

    public String getRandomCountry() {
        int randomNumber = getRandNum(1, 100);
        int propSum = 0;

        for (int i = 0; i < this.popProportionalBuckets.length; i++) {
            if (randomNumber < propSum) {
                return this.countryNames[i-1];
            } else {
                propSum += this.popProportionalBuckets[i];
            }
        }

        if (randomNumber < propSum) {
            return this.countryNames[this.popProportionalBuckets.length-1];
        }

        return "Nothing found! Weird..";
    }

    public int getRandNum(int min, int max) {
        Random rand = new Random();
        return rand.nextInt(max-min)+min;
    }
}