String similarity score using Java

StringSimilarityScore.java

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;
}
/* 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());
}