Custom Exception: Age Validation

/*
 * Problem : Process lines.
 * Input   : Several lines.
 * Output  : One line per age.
 * Approach: Custom exception class.
 * Time    : O(n)
 * Space   : O(n)
 * Java    : 8 or newer.
 */
import java.util.Scanner;

public class Main {
        // Step 1: A custom exception is a new class that extends Exception. The name tells what went wrong.
        static class InvalidAgeException extends Exception {
            InvalidAgeException(String message) {
                super(message);
            }
        }

        // Step 2: The method declares with "throws" that it can fail. It throws our exception for a bad age.
        static void checkAge(long age) throws InvalidAgeException {
            if (age < 0 || age > 150) {
                throw new InvalidAgeException("invalid age " + age);
            }
        }

    // This method solves the task. It receives the input and returns the answer.
    static String[] solve(String[] lines) {
        String[] output = new String[lines.length];
        for (int i = 0; i < lines.length; i++) {
            long age = Long.parseLong(lines[i]);

            // Step 3: Try the check. If it throws our exception, catch it and print its message.
            try {
                checkAge(age);
                output[i] = "ok " + age;
            } catch (InvalidAgeException error) {
                output[i] = error.getMessage();
            }
        }
        return output;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        java.util.List<String> all = new java.util.ArrayList<>();
        while (scanner.hasNextLine()) {
            String line = scanner.nextLine().trim();
            if (!line.isEmpty()) {
                all.add(line);
            }
        }
        String[] lines = all.toArray(new String[0]);
        System.out.println(String.join("\n", solve(lines)));
    }
}