Calculate the Jaccard Distance between two strings

JaccardDistance.java

import java.util.HashMap;

public class JaccardDistance {

    public static double jaccard(String a, String b) {
        HashMap<String, Integer> map = new HashMap<>();

        // For each bigram in first string, add 1
        for(int i=0; i < a.length()-1; i++) {
            String bigram = "" + a.charAt(i) + a.charAt(i+1);
            map.put(bigram, map.getOrDefault(bigram, 0) + 1);
        }

        // For each bigram in second string, reduce 1
        for(int i=0; i < b.length()-1; i++) {
            String bigram = "" + b.charAt(i) + b.charAt(i+1);
            map.put(bigram, map.getOrDefault(bigram, 0) - 1);
        }

        // Calculate elements in intersection
        int intersection = 0;
        int missingFromA = 0;
        for(int value : map.values()) {
            intersection += Math.abs(value);

            // Negative values are missing from A
            if (value < 0) {
                missingFromA += Math.abs(value);
            }
        }

        // Calculate elements in union
        int bigramsInA = a.length() - 1;
        int union = bigramsInA + missingFromA;

        return intersection/(double)union;
    }

    public static void main(String[] args) {
        System.out.println(jaccard(
                "The quick brown fox jumps over the lazy dog",
                "The quick brown fox jumps over the hazy dog"));
        // Result: 0.09090909090909091
    }
}