JAVA实现计算simhash距离的代码

以下是JAVA实现计算simhash距离的代码：

import java.math.BigInteger;
import java.util.StringTokenizer;

public class SimHash {

    private String tokens;
    private BigInteger hash;

    public SimHash(String tokens) {
        this.tokens = tokens;
        this.hash = this.simHash();
    }

    public BigInteger getHash() {
        return this.hash;
    }

    public int hammingDistance(SimHash other) {
        BigInteger x = this.hash.xor(other.hash);
        int distance = ;

        while (x.signum() != ) {
            distance += 1;
            x = x.and(x.subtract(BigInteger.ONE));
        }

        return distance;
    }

    private BigInteger simHash() {
        int[] v = new int[64];

        StringTokenizer tokenizer = new StringTokenizer(this.tokens);
        while (tokenizer.hasMoreTokens()) {
            String token = tokenizer.nextToken();
            BigInteger hash = HashUtil.hash(token);
            for (int i = ; i < 64; i++) {
                BigInteger bitmask = BigInteger.ONE.shiftLeft(i);
                if (hash.and(bitmask).signum() != ) {
                    v[i] += 1;
                } else {
                    v[i] -= 1;
                }
            }
        }

        BigInteger fingerprint = BigInteger.ZERO;
        for (int i = ; i < 64; i++) {
            if (v[i] >= ) {
                fingerprint = fingerprint.add(BigInteger.ONE.shiftLeft(i));
            }
        }

        return fingerprint;
    }

    public static void main(String[] args) {
        String s1 = "This is a test string for simhash";
        String s2 = "This is a test string for simhash, which is used to calculate the distance between two strings.";

        SimHash hash1 = new SimHash(s1);
        SimHash hash2 = new SimHash(s2);

        System.out.println(hash1.hammingDistance(hash2));
    }
}

class HashUtil {

    public static BigInteger hash(String str) {
        if (str == null || str.length() == ) {
            return BigInteger.ZERO;
        }

        char[] charArray = str.toCharArray();
        BigInteger x = BigInteger.valueOf(((long) charArray[]) << 7);

        long m = 1000003;
        long mask = (1L << 31) - 1;
        for (char c : charArray) {
            BigInteger temp = BigInteger.valueOf((long) c);
            x = x.multiply(BigInteger.valueOf(m)).xor(temp).and(BigInteger.valueOf(mask));
        }

        x = x.xor(BigInteger.valueOf(charArray.length));
        if (x.equals(BigInteger.valueOf(-1))) {
            x = BigInteger.valueOf(-2);
        }

        return x;
    }
}