二维数组

//计算接下来的年份
        for(int i = 1; i < balances.length ;i++)
        {
            for(int j = 0;j < balances[i].length; j++)
            {
                //获取本金结余
                double oldBalance = balances[i-1][j];
                //计算interest 本金*利率
                double interest = oldBalance * interestRate[j];
               // 计算下一年本金
                balances[i][j] = interest + oldBalance;
            }
        }