Java Code:Underline keyword in sentence

1:    public String markWord(String sentence, String word) {  
2:      int lastFound = -1;  
3:      while ((lastFound = sentence.toLowerCase().indexOf(word, lastFound)) > -1) {  
4:          String prefix=sentence.substring(0, lastFound) + "<u><b>";  
5:          String _word= sentence.substring(lastFound,lastFound+ word.length());  
6:          String suffix="</b></u>"  
7:              + sentence.substring(lastFound + word.length(), sentence.length());  
8:          sentence = prefix+_word+suffix;  
9:          lastFound+="<u><b></b></u>".length();  
10:      }  
11:      return sentence;  
12:    }