How to split a string to non empty words if it might include a separator like tab on first place

may help you . You can just use the String.split(..) method, no need for StringUtils:

"a,,h".split(","); // gives ["a", "", "h"]

it fixes the issue Use list():

>>> list('1111')
['1', '1', '1', '1']

>>> map(None, '1111')
['1', '1', '1', '1']

$ python -m timeit "list('1111')"
1000000 loops, best of 3: 0.483 usec per loop
$ python -m timeit "map(None, '1111')"
1000000 loops, best of 3: 0.431 usec per loop

around this issue This is not a linear problem. Among other difficulties, some character sequences can be separated into more than one reasonable string of words.
However, the approach is straightforward with a recursive routine. Go through your lexicon (dictionary of legal words) and find each word you can form from the start of the given sentence. Iterate through those words; for each, parse the rest of the sentence. If successful, return the properly separated input (current word + parsing of the remainder).

// Parse a character sequence
//   return a list of legal word separations
// Assume a word list, lexicon, as a global
sep_string(str sentence)
    result = <empty list>
    sent_size = length of sentence

    for word_size in 1:sent_size
        word = sentence[0:word_size-1]  // next potential word

        if word in lexicon
            // Found a legal word; remove it and parse
            //   the rest of the sequence
            sep_rest = sep_string(sentence[word_size:sent_size])
            // sep_rest is a list of parsings for
            //   the rest of the sequence

            for each solution in sep_rest
                append (word + " " + solution) to result

    return result