Java recursive(?) repeated(?) deep(?) pattern matching

Question

I\'m trying to get ALL the substrings in the input string that match the given pattern.

For example,

Given string: aaxxbbaxb
Pa

Answer 1

you are in effect searching for the strings ab, a_b, and a__b in an input string, where _ denotes a non-whitespace character whose value you do not care about.

That's three search targets. The most efficient way I can think of to do this would be to use a search algorithm like the Knuth-Morris-Pratt algorithm, with a few modifications. In effect your pseudocode would be something like:

for i in 0 to sourcestring.length
    check sourcestring[i] - is it a? if so, check sourcestring[i+x] 
       // where x is the index of the search string - 1
    if matches then save i to output list
    else i = i + searchstring.length

obviously if you have a position match you must then check the inner characters of the substring to make sure they are alphabetical.

run the algorithm 3 times, one for each search term. It will doubtless be much faster than trying to do the search using pattern matching.

edit - sorry, didn't read the question properly. If you have to use regex then the above will not work for you.