String x2 = "hello";
String newSortedString = "";
Object[] y = x2.toLowerCase()
                .chars()
                .sorted()
                .mapToObj(i -> (char) i)
                .toArray();

for (Object o: y) {
  newSortedString = newSortedString.concat(o.toString());
}

System.out.println(newSortedString);