public class Main {
    public static void main(String[] args) {
        // 给一个有工资收入和稿费收入的小伙伴算税
        Income[] incomes = {new Income(3000), new SalaryIncome(7500), new RoyaltyIncome(12000)};
        System.out.println(totalTax(incomes));
    }

    /**
     * 计算总税费
     * @param incomes
     * @return double
     */
    public static double totalTax(Income[] incomes) {
        double total = 0;
        for (Income income : incomes) {
            total += income.getTax();
        }
        return total;
    }
}

class Income {
    protected final double income;

    public Income(double income) {
        this.income = income;
    }

    public double getTax() {
        return income * 0.1;
    }
}


/**
 * 工资收入税率
 */
class SalaryIncome extends Income {

    public SalaryIncome(double income) {
        super(income);
    }

    @Override
    public double getTax() {
        if (income <= 5000) {
            return 0;
        }
        return (income - 5000) * 0.2;
    }
}


/**
 * 稿费收入税率
 */
class RoyaltyIncome extends Income {
    public RoyaltyIncome(double income) {
        super(income);
    }

    @Override
    public double getTax() {
        return income * 0.2;
    }
}