String fdbs = "a,c,b,d";
String[] str = fdbs.split(",");
Set set = new TreeSet();
for (int i = 0; i < str.length; i++) {
set.add(str[i]);
}
str = (String[]) set.toArray(new String[0]);
for (int i = 0; i < str.length; i++) {
System.out.println(str[i]);
}