Custom Exception: Insufficient Funds

/*
 * Problem : Process lines.
 * Input   : Several lines.
 * Output  : One result per command.
 * Approach: Own exception class.
 * Time    : O(n)
 * Space   : O(1)
 * Java    : 8 or newer.
 */
import java.util.Scanner;

public class Main {
        // Step 1: Our own checked exception. It carries the missing amount as extra data.
        static class InsufficientFundsException extends Exception {
            private final long missing;

            InsufficientFundsException(long missing) {
                super("short by " + missing);
                this.missing = missing;
            }

            long getMissing() {
                return missing;
            }
        }

        static class Account {
            private long balance = 0;

            long deposit(long amount) {
                balance += amount;
                return balance;
            }

            // Step 2: "throws" tells the caller that this method can fail. The caller must handle it.
            long withdraw(long amount) throws InsufficientFundsException {
                if (amount > balance) {
                    throw new InsufficientFundsException(amount - balance);
                }
                balance -= amount;
                return balance;
            }
        }

    // This method solves the task. It receives the input and returns the answer.
    static String[] solve(String[] lines) {
        Account account = new Account();
        String[] output = new String[lines.length];
        for (int i = 0; i < lines.length; i++) {
            String[] part = lines[i].split(" ");
            long amount = Long.parseLong(part[1]);
            // Step 3: Catch our own exception and read the data it carries.
            try {
                long balance = part[0].equals("deposit") ? account.deposit(amount) : account.withdraw(amount);
                output[i] = "balance " + balance;
            } catch (InsufficientFundsException error) {
                output[i] = "error: short by " + error.getMissing();
            }
        }
        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)));
    }
}