Find repeating sub-sequences in a string

This is a problem given by Peng Li (http://allenlipeng47.com/PersonalPage/index/list/1/nkey)
Given a string , find if there is any sub-sequence that repeats itself. Here, sub-sequence can be a non-contiguous pattern, with the same relative order. 

1. abab <------yes, ab is repeated
2. abba <---- No, a and b follow different order
3. acbdaghfb <-------- yes there is a followed by b at two places
4. abcdacb <----- yes a followed by b twice
5. aacc< ----yes, aacc, the underline ‘ac’ and red ‘ac’ are the repeating sub-sequences.

We can reduce this problem to the problem of finding common sub-sequence amount two strings, in this case, the two strings are identical. Also note the diagonal values of the DP table will be the string itself or identical sub-sequences which we should not consider.

For example:

negative example: abba

before and after we set diagonal values to 0

len(sub-seq)	a	b	b	a
a	1	1	1	2
b	1	2	2	2
b	1	2	3	3
a	1	2	3	4

len(sub-seq)	a	b	b	a
a	0	0	0	1
b	0	0	1	1
b	0	1	0	1
a	1	1	1	0

positive example: abab

len(sub-seq)	a	b	a	b
a	0	0	1	1
b	0	0	1	2
a	1	1	0	2
b	1	2	2	0

public static boolean findLongestSubsequence(String s1, String s2){

 int len1 = s1.length(), len2 = s2.length();

//part1 build DP table bottom-up

 int[][] table = new int[len1+1][len2+1];

     

 for(int i = 1; i<len1+1; i++){

     for(int j=1; j<len2+1; j++){

          if(i!=j){ <=== can not consider the subsequence sharing the same characters

          if(s1.charAt(i-1) == s2.charAt(j-1))

            table[i][j] = table[i-1][j-1]+1;

          else

            table[i][j] = Math.max(table[i-1][j], table[i][j-1]);        

          }

     }

 } 

  for(int i = 0; i<len2+1; i++){

     if(table[len1][i]>1)

        return true;

  }  

return false;

}