Clock Time Class

/*
 * Problem : Run the commands.
 * Input   : Command lines.
 * Output  : One line per answer.
 * Approach: Time class
 * Time    : O(n)
 * Space   : O(n)
 * Java    : 8 or newer.
 */
import java.util.Scanner;

public class Main {
        // Step 1: A Time keeps one number: the minutes since midnight. It never changes after it is created.
        static class Time {
            private final int minutes;

            Time(int minutes) {
                this.minutes = minutes;
            }

            // Step 2: Moving forward gives a new Time. The remainder makes the clock wrap.
            Time plus(int extra) {
                return new Time((minutes + extra) % 1440);
            }

            int until(Time other) {
                return ((other.minutes - minutes) % 1440 + 1440) % 1440;
            }

            String text() {
                return String.format("%02d:%02d", minutes / 60, minutes % 60);
            }
        }

    // This method solves the task. It receives the input and returns the answer.
    static String[] solve(String[] lines) {
        java.util.Map<String, Time> times = new java.util.HashMap<String, Time>();
        java.util.List<String> out = new java.util.ArrayList<String>();
        for (String line : lines) {
            String[] part = line.split(" ");
            if (part[0].equals("set")) {
                String[] clock = part[2].split(":");
                times.put(part[1], new Time(Integer.parseInt(clock[0]) * 60 + Integer.parseInt(clock[1])));
            } else if (part[0].equals("add")) {
                times.put(part[1], times.get(part[1]).plus(Integer.parseInt(part[2])));
            } else if (part[0].equals("diff")) {
                out.add(String.valueOf(times.get(part[1]).until(times.get(part[2]))));
            } else {
                out.add(times.get(part[1]).text());
            }
        }
        return out.toArray(new String[0]);
    }

    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)));
    }
}