Armstrong numbers in a given range using Java 8

Question

Was fiddling with java-8; trying to write a program for getting all Armstrong Numbers between 1 and 10_000_000.

Following is my working solution:

public class ArmstrongNumbers {
 public static void main(String[] args) {
 IntStream.range(1, 10_000_000)
 .filter((n) -> {
 int c = 0, temp = n;
 while (temp > 0) {
 c += Math.pow(temp % 10, Integer.toString(n).length());
 temp /= 10;
 }
 return c == n;
 }).forEach(System.out::println);
 }
}

Output:

1
2
3
4
5
6
7
8
9
153
370
371
407
1634
8208
9474
54748
92727
93084
548834
1741725
4210818
9800817
9926315

Why I'm here:

• Can this be made shorter?
• Can any other Java 8 concept be used here?
• Can the use of the while loop be avoided and a stream be used somehow (given that it is more elegant)?
• Review overall correctness

Here is a link to a list of Armstrong Numbers for verifying the outputs.

Please note that there is a follow up question.

• Bilesh Ganguly: Follow up question: codereview.stackexchange.com/q/134734/104662

Answer 1

Integer.toString(n).length() can be assigned to its own variable.

If you wanted to stream the while loop, I suppose you could split a toString() version of the number via toCharArray() and then calculate the value for each digit individually, then summing the result via the sum function.

I don't know whether that'd qualify as "more elegant", though. You would get rid of c and temp as variables by doing that.

• Bilesh Ganguly: Made changes as per your suggestion. Should I share it as an update to the question?
• Bilesh Ganguly: Follow up question: codereview.stackexchange.com/q/134734/104662