Ratcliff/Obershelp pattern recognition in Java

I needed a way to compare the similarity of two strings and return value as a percentage in a project, so I implemented a Java version of the Ratcliff/Obershelp pattern regocnition algorithm and thought I'd share it here. The definition of the algorithm is as follows:

"Compute the similarity of two strings as the doubled number of matching characters divided by the total number of characters in the two strings. Matching characters are those in the longest common subsequence plus, recursively, matching characters in the unmatched region on either side of the longest common subsequence."

The returned value ranges from 0..1f. Below is the source, enjoy :)

public class Simil {

 public Simil() {};
 
 private static float tcnt;
 
 private void findSubstr(String s1, int s1len, String s2, int s2len, Struct ss) {
  int size = 1;
  
  ss.setO2(-1);
  
  for (int i = 0; i < (s1len - size); i++) {
   for (int j = 0; j < (s2len - size); j++) {
    int test_size = size;
    
    while (true) {
     if ((test_size <= (s1len - i)) && (test_size <= (s2len - j))) {
      if (s1.regionMatches(i, s2, j, test_size)) {
       if (test_size > size || ss.getO2() < 0) {
        ss.setO1(i);
        ss.setO2(j);
        size = test_size;
       }
       test_size++;
      } else {
       break;
      }
     } else {
      break;
     }
    }
   }
  }
  
  if (ss.getO2() < 0) {
   ss.setLen(0);   
  } else {
   ss.setLen(size);
  }
 }
 
 private void rsimil(String s1, int s1len, String s2, int s2len) {
  Struct ss = new Struct();
  
  if (s1len == 0 || s2len == 0) return;
  
  findSubstr(s1, s1len, s2, s2len, ss);
  
  if (ss.getLen() > 0) {
   int delta1, delta2;
   tcnt += ss.getLen() << 1;
   rsimil(s1, ss.getO1(), s2, ss.getO2());
   
   delta1 = ss.getO1() + ss.getLen();
   delta2 = ss.getO2() + ss.getLen();
   
   if (delta1 < s1len && delta2 < s2len) {
    rsimil(s1.substring(delta1, s1len), s1len - delta1, s2.substring(delta2, s2len), s2len - delta2);
   }
  }
  
 }
 
 public float ratcliff(String s1, String s2) {
  int s1len, s2len;
  float tlen;
  
  if (s1 == null || s2 == null) {
   return 0;
  } else if (s1.equals(s2)) {
   return 1;
  }
  
  s1 = s1.toLowerCase();
  s2 = s2.toLowerCase();
  
  s1len = s1.length();
  s2len = s2.length();
  
  tcnt = 0;
  tlen = s1len + s2len;
  
  rsimil(s1, s1len, s2, s2len);
  
  return tcnt / tlen;
 }
 
 class Struct {
  Struct() {};
  
  int o1, o2, len;

  public int getLen() {
   return len;
  }

  public void setLen(int len) {
   this.len = len;
  }

  public int getO1() {
   return o1;
  }

  public void setO1(int o1) {
   this.o1 = o1;
  }

  public int getO2() {
   return o2;
  }

  public void setO2(int o2) {
   this.o2 = o2;
  }  
 }
}