过滤字符串中的HTML符号

public class StringUtil{

            public static String filterHTML(String input){

                      if (input == null ){

                                 return null;

                      }

                      if (input.length() == 0){

                                 return input;

                       }

                       input = input.replaceAll("&", "&");

                       input = input.replaceAll("<", "&lt;");

                       input = input.replaceAll(">", "&gt;");

                       input = input.replaceAll(" " , "&nbsp;");

                       input = input.replaceAll("'', "&#39;");

                       input = input.replaceAll("\"", "&quot;");

                       input = input.replaceAll("\n", "<br>");

                       return input;

             }

}