Not necessary. There's a simple trick that makes it lightning fast.

That being said, the lower bound is effectively 0.

plz provide upper and lower bound

how you solve this.i got time limit

Unit test for 1021 have mistake. Should return 1201

getting "DescendingOrder.java:30: error: reached end of file while parsing" but it seems my code work fine.
whats wrong here?
import java.util.ArrayList;
import java.util.Collections;
public class DescendingOrder {
public static int sortDesc(final int num) {
ArrayList list = new ArrayList();
StringBuilder stringBuilder = new StringBuilder();
int num1 = num;
if (num1 < 10) {
return num1;
} else {
while (num1 != 0) {
int n = num1 % 10;
num1 = num1 / 10;
list.add(n);

        }
        Collections.sort(list);
        Collections.reverse(list);
        int len = list.size();
        //System.out.println(len);
        for (Integer i : list
                ) {
            stringBuilder.append(String.valueOf(i));

        }
        String s = stringBuilder.toString();
        int n = Integer.parseInt(s);
        return n;

}
}