Generate a String similarity score with Java

Here is a way to generate a String similarity score using Java:

/* Generates number between 0.00 and 1.00 */
public double stringSimilarityScore(List<char[]> bigram1, List<char[]> bigram2) {
    List<char[]> copy = new ArrayList<char[]>(bigram2);
    int matches = 0;
    for (int i = bigram1.size(); --i >= 0;) {
        char[] bigram = bigram1.get(i);
        for (int j = copy.size(); --j >= 0;) {
            char[] toMatch = copy.get(j);
            if (bigram[0] == toMatch[0] && bigram[1] == toMatch[1]) {
                copy.remove(j);
                matches += 2;
                break;
            }
        }
    }
    return (double) matches / (bigram1.size() + bigram2.size());
}

And the supporting method:

public List<char[]> bigram(String input) {
    ArrayList<char[]> bigram = new ArrayList<char[]>();
    for (int i = 0; i < input.length() - 1; i++) {
        char[] chars = new char[2];
        chars[0] = input.charAt(i);
        chars[1] = input.charAt(i+1);
        bigram.add(chars);
    }
    return bigram;
}