java中的数据结构

import java.util.ArrayList;
import java.util.List;

class Item {
    private int count;
    public Item(int count) {
        this.count = count;
    }
    public int getCount() {
        return count;
    }

}

class Meal {
    private ArrayList<Item> items = new ArrayList<Item>();

    void addItem(Item item) {
        items.add(item);
    }

    int sum_count() {
        int count =  0;
        for (Item i : items) {
            count += i.getCount();
        }
        return count;
    }

}

public class BuilderPatternDemo {
    public static void main(String args[]) {
        Item item1 = new Item(10);
        Item item2 = new Item(20);
        Item item3 = new Item(30);

        Meal meal1 = new Meal();

        meal1.addItem(item1);
        meal1.addItem(item2);
        meal1.addItem(item3);
        System.out.println("Sum=" + meal1.sum_count());
    }
}