How to avoid out of memory error in string builder in android

[vijayakumar durai]

Hi friends
I am getting out of memory error in string builder in android .I am gettin lot of values from webservice while replacing xml entity character reference character i used stringbuffer .How to avoid that can anybody give example how to do?

My appending code

 public  String unescapeXML(String str) {
    	 StringBuffer buf=null;
    	     if (str == null || str.length() == 0)
          return "";

         buf = new StringBuffer();
        int len = str.length();
        for (int i = 0; i < len; ++i) {
          char c = str.charAt(i);
          if (c == '&') {
            int pos = str.indexOf(";", i);
            if (pos == -1) { // Really evil
              buf.append('&');
            } else if (str.charAt(i + 1) == '#') {
              int val = Integer.parseInt(str.substring(i + 2, pos), 16);
              buf.append((char) val);
              i = pos;
            } else {
              String substr = str.substring(i, pos + 1);
              if (substr.equals("&"))
                buf.append('&');
              else if (substr.equals("<"))
                buf.append('<');
              else if (substr.equals(">"))
                buf.append('>');
              else if (substr.equals("""))
                buf.append('"');
              else if (substr.equals("'"))
                buf.append('\'');
              else if (substr.equals(" "))
            	  buf.append(" ");
                                         
              else
                // ????
                buf.append(substr);
              i = pos;
            }
          } else {
            buf.append(c);
             
          }
                              
        }
        return buf.toString(); 
      }