Java library for free-text diff [closed]

Answer 1

If you're example is really what you want to do - ie subsequences only match if they start at the same index (which is different from how diffs normally operate) - this is all you need to do:

import java.util.*;

class StringDiff {
    public static List from(String s1, String s2) {
        int start = -1;
        int pos = 0;
        LinkedList list = new LinkedList();

        for(; pos < s1.length() && pos < s2.length(); ++pos) {
            if(s1.charAt(pos) == s2.charAt(pos)) {
                if(start < 0) start = pos;
            }
            else {
                if(start >= 0) list.add(new int[] { start, pos });
                start = -1;
            }
        }

        if(start >= 0) list.add(new int[] { start, pos });

        return list;
    }

    public static void main(String[] args) {
        for(int[] idx : from(args[0], args[1]))
            System.out.println(args[0].substring(idx[0], idx[1]));
    }
}

An actual diff implementation will be far more sophisticated.