@Override
    public String toString() {
        StringBuffer buffer = new StringBuffer();
        int i=0;
        for(SuffixNode node : child){
            if(node != null){
                buffer.append((char)i + " ");
            }
            i++;
        }
        return "SuffixNode [start=" + start + "]" + " " + buffer.toString();
    }
Do validation of the tree by comparing all suffixes and their index at leaf node.
src/com/interview/suffixprefix/SuffixTree.java