JAVACore chapter3 - demo 7-8

如何声明一二维数组，并使用for循环处理二维数组

package corejava.chapter3;


/**
 * @Auther WangYu
 * @Date 2022/3/5
 * 声明一个二维数组
 */
public class CompoundInterest {
    public static void main(String[] args) {
        final double STARTRATE = 10;
        final int NRATES = 6;
        final int NYEARS = 10;

        //设置利率为10...15%
        double[] interestRate = new double[NRATES];
        for (int j = 0; j < interestRate.length; j++) {
            interestRate[j] = (STARTRATE + j) / 100.0;
        }

        double[][] balances = new double[NYEARS][NRATES];

        //设置初始balances为10000
        for (int j = 0; j < balances[0].length; j++) {
            balances[0][j] = 10000;
        }

        //为未来几年计算利率
        for (int i = 1; i < balances.length; i++) {
            for (int j = 0; j < balances[i].length; j++) {
                //从上一年中获取当前的行数
                double oldBalance = balances[i - 1][j];
                //计算利率
                double interest = oldBalance * interestRate[j];
                //计算这一年的收益
                balances[i][j] = oldBalance + interest;
            }
        }

        //打印一行利率
        for (int j = 0; j < interestRate.length; j++) {
            //将输出的数据进行格式化
            System.out.printf("%9.0f%%", 100 * interestRate[j]);
            System.out.println();
        }

        // 打印平衡利率表
        for (double[] row : balances) {
            //print table row
            for (double b : row){
                System.out.printf("%10.2f", b);
                System.out.println();
            }
        }
    }
}