Decorator: Coffee with Extras

/*
 * Problem : Process lines.
 * Input   : Several lines.
 * Output  : Description and price.
 * Approach: Wrap drinks.
 * Time    : O(total words)
 * Space   : O(n)
 * Java    : 8 or newer.
 */
import java.util.Scanner;

public class Main {
        // Step 1: A Drink has a description and a price. Every extra wraps another Drink.
        interface Drink {
            String description();

            long price();
        }

        static class Plain implements Drink {
            private final String name;
            private final long cost;

            Plain(String name, long cost) {
                this.name = name;
                this.cost = cost;
            }

            public String description() {
                return name;
            }

            public long price() {
                return cost;
            }
        }

        // Step 2: A decorator holds a drink inside. It adds its own name and price to the inner drink.
        static class Extra implements Drink {
            private final Drink inner;
            private final String name;
            private final long cost;

            Extra(Drink inner, String name, long cost) {
                this.inner = inner;
                this.name = name;
                this.cost = cost;
            }

            public String description() {
                return inner.description() + "+" + name;
            }

            public long price() {
                return inner.price() + cost;
            }
        }

    // This method solves the task. It receives the input and returns the answer.
    static String[] solve(String[] lines) {
        java.util.Map<String, Long> extras = new java.util.HashMap<>();
        extras.put("milk", 50L);
        extras.put("sugar", 10L);
        extras.put("whip", 70L);

        String[] output = new String[lines.length];
        for (int i = 0; i < lines.length; i++) {
            String[] parts = lines[i].split(" ");

            // Step 3: Start with the base drink.
            Drink drink = new Plain(parts[0], parts[0].equals("espresso") ? 300 : 200);

            // Step 4: Wrap the drink once for each extra. The last wrapper is the outer one.
            for (int j = 1; j < parts.length; j++) {
                drink = new Extra(drink, parts[j], extras.get(parts[j]));
            }
            output[i] = drink.description() + " " + drink.price();
        }
        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)));
    }
}