Safe Calculator (Exception Handling)

/*
 * Problem : Process commands line by line.
 * Input   : Several lines of commands.
 * Output  : One line for each input line.
 * Approach: Catch the exceptions.
 * Time    : O(lines)
 * Space   : O(lines)
 * Java    : 8 or newer.
 */
import java.util.Scanner;

public class Main {
    // 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++) {
            String[] parts = lines[i].split("\\s+");

            // Step 1: Try to do the work. Any problem becomes an exception.
            try {
                // Step 2: Integer.parseInt throws NumberFormatException for bad text. A missing part throws ArrayIndexOutOfBoundsException.
                long a = Long.parseLong(parts[0]);
                String operator = parts[1];
                long b = Long.parseLong(parts[2]);

                switch (operator) {
                    case "+":
                        output[i] = String.valueOf(a + b);
                        break;
                    case "-":
                        output[i] = String.valueOf(a - b);
                        break;
                    case "*":
                        output[i] = String.valueOf(a * b);
                        break;
                    case "/":
                        // Step 3: Dividing by zero throws ArithmeticException. Java long division cuts toward zero.
                        output[i] = String.valueOf(a / b);
                        break;
                    default:
                        output[i] = "Error: unknown operator";
                }
            } catch (ArithmeticException error) {
                output[i] = "Error: division by zero";
            } catch (NumberFormatException | ArrayIndexOutOfBoundsException error) {
                // Step 4: Handle several exception types in one catch block.
                output[i] = "Error: bad input";
            }
        }
        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)));
    }
}