哈希码如何在内部创建？

Question

有人告诉我如何 java 在内部创建哈希码吗？

package swain.javainterviewhub.blogspot.in;


    public class JavaInterviewHub {

        public static  void main(String[] args) {

           String str="Alex";
           System.out.println(str.hashCode());
        }

    }
    Output:2043454

密钥哈希码算法哈希码

亚历克斯 A(1) + L(12) + E(5) + X(24)=42

Answer 1

来自documentation：

The hash code for a String object is computed as
 s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]

您还可以查看源代码以获取更多信息（此处为 Oracle JDK 8u45）。

public int hashCode() {
    int h = hash;
    if (h == 0 && value.length > 0) {
        char val[] = value;

       for (int i = 0; i < value.length; i++) {
            h = 31 * h + val[i];
        }
        hash = h;
    }
    return h;
}

Answer 2

Java 中的哈希码生成取决于相关对象的类型。对于字符串，算法在 Java 文档 (here) 中进行了描述。

Returns a hash code for this string. The hash code for a String object is computed as

 s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]

using int arithmetic, where s[i] is the ith character of the string, n is the length of the string, and ^ indicates exponentiation. (The hash value of the empty string is zero.)

哈希码如何在内部创建？

How hashcode create in internally?

java

object

hashcode