Text Justification

public class Solution {
    public ArrayList<String> fullJustify(String[] words, int L) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        int wordsCount = words.length;
        ArrayList<String> result = new ArrayList<String>();
        int curLen = 0;
        int lastI = 0;
        for (int i = 0; i <= wordsCount; i++) {
            if (i == wordsCount || curLen + words[i].length() + i - lastI > L) {
                StringBuffer buf = new StringBuffer();
                int spaceCount = L - curLen;
                int spaceSlots = i - lastI - 1;
                if (spaceSlots == 0 || i == wordsCount) {
                    for(int j = lastI; j < i; j++){
                        buf.append(words[j]);
                        if(j != i - 1)
                            appendSpace(buf, 1);
                    }
                    appendSpace(buf, L - buf.length());
                } else {
                    int spaceEach = spaceCount / spaceSlots;
                    int spaceExtra = spaceCount % spaceSlots;
                    for (int j = lastI; j < i; j++) {
                        buf.append(words[j]);
                        if (j != i - 1)
                            appendSpace(buf, spaceEach + (j - lastI < spaceExtra ? 1 : 0));
                    }
                }
                result.add(buf.toString());
                lastI = i;
                curLen = 0;
            }
            if (i < wordsCount)
                curLen += words[i].length();
        }
        return result;
    }

    private void appendSpace(StringBuffer sb, int count) {
        for (int i = 0; i < count; i++)
            sb.append(' ');
    }
}