Java简单加密，输出略有不同

Question

我编写了这个简单的加密程序：

public static void main(String[] args) {
    int password = 123456789;
    int firstLayer = password / 58;
    int secondLayer = firstLayer * 23;
    int thirdLayer = secondLayer + 85;
    System.out.println(thirdLayer);

    int encryptedPassword = thirdLayer;
    int thirdLayerD = encryptedPassword - 85;
    int secondLayerD = thirdLayerD / 23;
    int firstLayerD = secondLayerD * 58;


    System.out.println(firstLayerD);

}

但我有一个奇怪的问题。解密密码后，我得到：123456770

我希望获得与原版相同的密码，但我不知道问题所在。

Answer 1

这是因为123456789/58 = 2128565,32759，这会被截断为一个int。

Answer 2

整数除法运算导致截断任何余数。

使用double，然后再次调用Math.round()生成整数：

public static void main(String[] args) {
    int password = 123456789;
    double firstLayer = password / 58d;
    double secondLayer = firstLayer * 23;
    double thirdLayer = secondLayer + 85;
    double encryptedPassword = thirdLayer;

    double thirdLayerD = encryptedPassword - 85;
    double secondLayerD = thirdLayerD / 23;
    int firstLayerD = (int)Math.round(secondLayerD * 58);

    System.out.println(firstLayerD);
}

输出：

123456789