Java 数组校验和与元素顺序无关

Question

假设我有两个数组，例如[B,D,C,A] 和 [B,A,D,C]。什么机制可以在两个数组(以及任何包含其元素排列的数组)上生成相同的校验和？

在以下示例中，check_a 和 check_b 不相等。将元素按字母顺序排列不是一个选项，因为数组中的对象可能不是字符串或任何可排序的东西。

String[] a = {"B","D","C","A"};
String[] b = {"B","A","D","C"};

String check_a = a.hashCode();
String check_b = b.hashCode();

Answer 1

简单示例

public class ArrayHash {

    public static void main(String[] args) {
        String[] one = new String[]{"A", "B", "C", "D"};
        String[] two = new String[]{"D", "C", "B", "A"};
        System.out.println("One = " + one.hashCode());
        System.out.println("Two = " + two.hashCode());
        System.out.println("Method for one = "+hash(one));
        System.out.println("Method for two = "+hash(two));
    }

    private static int hash(Object[] array) {
        int ret = 0;
        for (Object c : array) {
            ret += (124567890 + c.hashCode()) * c.hashCode();
        }
        return ret;
    }
}

它给出了输出

One = 366712642
Two = 1829164700
Method for one = 266
Method for two = 266

如您所见，您必须迭代所有元素并对它们的哈希值求和(或相乘)。无论它们的顺序如何，都会给你相同的结果。