java - hashcode是内存地址还是内存地址内容的整数？

Question

为什么这段代码给出负的哈希码？

import java.util.HashSet;
import java.util.Set;

public class Ab {

    /**
     * @param args
     */
    public static void main(String[] args) {
    String s1="Operations on a dynamic set can be grouped into two categories queries, which simply return information about the set, and modifying operations, which change the set. Here is a list of typical operations. Any specific application will usually   require only a few of these to be implemented Some dynamic sets presuppose that the keys are drawn from a totally ordere, such as the real numbers, or the set of all words under the usual alphabetic ordering. A total ordering allows us to define the minimum element of the set, for example, or to speak of the next element larger than a given element in a set.Operations on dynamic sets Operations on a dynamic set can be grouped into two categories: q";

    System.out.println(s1.hashCode());
    String s2="abc";
    System.out.println(s2.hashCode());
    }

}

Answer 1

String 类重写 hashCode() 以产生确定性结果。结果与内存地址无关。 String.hashCode() Javadoc显示用于计算它的公式:

The hash code for a String object is computed as s[0]*31^(n-1) + s1*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.)

请注意，即使对于相对较短的字符串，该值对于整数来说也可能太大。在计算过程中，每当发生溢出时，仅保留最低有效的 32 位。 在计算结束时，如果设置了结果整数的最高有效位，则该整数为负数，否则为正数。