Simulates return and results on the SunExchange

SunExchangeCalculator.java

package com.helospark.invest;

import java.util.ArrayList;
import java.util.List;

/**
 * Simulates return and results on the SunExchange.
 */
public class SunExchangeCalculator {
    private static final double ZAR_TO_USD = 0.066;
    private static final int CELL_LIFETIME = 20;
    private static final double PRICE_PER_CELL_ZAR = 78.0;
    private static final double WATT_PER_CELL = 5;
    private static double INITIAL_INVESTEMENT_USD = 1000.0;
    private static double ADDITIONAL_INVESTEMENT_PER_YEAR = 0.0; // add this investement every year
    private static int SIMULATION_YEARS = 30;
    private static int REINVESTEMENT_UNTIL_YEAR = 30; // reinvest all earnings from the investement back into thesunexchange until this years
    private static double START_EARNINGS_IN_ZAR_PER_CELL = 5;
    private static final double INTEREST_INCREASE_PER_YEAR = 1.075;
    
    static double money = 0.0;

    static List<Integer> numberOfCellsPerYear = new ArrayList<>();

    public static void main(String[] args) {
        int numberOfCellsForFirstYear = (int) ((INITIAL_INVESTEMENT_USD / ZAR_TO_USD) / PRICE_PER_CELL_ZAR);
        
        numberOfCellsPerYear.add(numberOfCellsForFirstYear);

        System.out.printf("%s\t\t%s\t\t%s\t\t%s\t\t%s\n", "Year", "Sum", "Earning", "# Cells", "Power capacity");
        for (int year = 0; year < SIMULATION_YEARS; ++year) {
            double fullEarningPerYear = 0.0;
            int startIndex = numberOfCellsPerYear.size() < CELL_LIFETIME ? 0 : numberOfCellsPerYear.size() - CELL_LIFETIME;
            for (int i = startIndex; i < numberOfCellsPerYear.size(); ++i) {
                double pricePerCell = (START_EARNINGS_IN_ZAR_PER_CELL * Math.pow(INTEREST_INCREASE_PER_YEAR, (year - i)));
                double earning = numberOfCellsPerYear.get(i) * pricePerCell;
                money += earning;
                fullEarningPerYear += earning;
            }
            
            money += (ADDITIONAL_INVESTEMENT_PER_YEAR / ZAR_TO_USD);
            
            if (year < REINVESTEMENT_UNTIL_YEAR) {
                int numberOfNewCells = (int)(money / PRICE_PER_CELL_ZAR);
                
                money -= numberOfNewCells * PRICE_PER_CELL_ZAR;
                
                numberOfCellsPerYear.add(numberOfNewCells);
            } else {
                numberOfCellsPerYear.add(0);
            }

            int numberOfCells = calculateNumberOfCells(numberOfCellsPerYear);
            System.out.printf("%d\t\t$%.1f\t\t$%.1f\t\t%d\t\t%.2fKW\n", (year + 1), (money * ZAR_TO_USD), (fullEarningPerYear * ZAR_TO_USD), numberOfCells, (numberOfCells * WATT_PER_CELL) / 1000.0);
        }
    }

    private static int calculateNumberOfCells(List<Integer> numberOfCellsPerYear) {
        int startIndex = numberOfCellsPerYear.size() < CELL_LIFETIME ? 0 : numberOfCellsPerYear.size() - CELL_LIFETIME;
        int sum = 0;
        for (int i = startIndex; i < numberOfCellsPerYear.size(); ++i) {
                sum += numberOfCellsPerYear.get(i);
        }
        return sum;
    }
}