2020.12.1收获

从今天开始想完成一个关于图书购物车的小型项目：

bean->Book.java （图书实体)

public class Book{
	
	private String id;
	private String name;
	private String author;
	private String description;
	private double price;
	
	public Book() {}
	public Book(String id,String name,String author,String description,double price) {
		this.id =id;
		this.name=name;
		this.author=author;
		this.description=description;
		this.price=price;
	}
	
	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getAuthor() {
		return author;
	}
	public void setAuthor(String author) {
		this.author = author;
	}
	public String getDescription() {
		return description;
	}
	public void setDescription(String description) {
		this.description = description;
	}
	public double getPrice() {
		return price;
	}
	public void setPrice(double price) {
		this.price = price;
	}
}

bean->CartItem.java（购物项实体）

    /*购物项代表的是当前书，并表示该书出现了几次*/
    public class CartItem {
    
        private Book book;
        private int quantity;
    
        //该购物项（书--不一定只有一本）的价钱应该等于书的数量*价格
        private double price;
    
        
        //书的价钱*数量
        public double getPrice() {
            return book.getPrice() * this.quantity;
        }
    
        public Book getBook() {
            return book;
        }
    
        public void setBook(Book book) {
            this.book = book;
        }
    
        public int getQuantity() {
            return quantity;
        }
    
        public void setQuantity(int quantity) {
            this.quantity = quantity;
        }
        
        public void setPrice(double price) {
            this.price = price;
        }
    }

bean->Cart.java（购物车实体)

    /*该类代表的是购物车*/
    public class Cart {
    
        //关键字是书籍的id，值是书
        private Map<String, CartItem> bookMap = new LinkedHashMap<>();
    
        //代表着购物车的总价
        private double price;
    
    
        //把购物项（用户传递进来的书籍）加入到购物车里边去，也应该是购物车的功能
        public void addBook(Book book) {
    
            //获取得到购物项
            CartItem cartItem = bookMap.get(book.getId());
    
            //判断购物车是否存在该购物项，如果不存在
            if (cartItem == null) {
    
                //创建这个购物项对象
                cartItem = new CartItem();
    
                //将用户传递过来的书籍作为购物项
                cartItem.setBook(book);
    
                //把该购物项的数量设置为1
                cartItem.setQuantity(1);
    
                //把购物项加入到购物车去
                bookMap.put(book.getId(), cartItem);
            } else {
    
                //如果存在该购物项，将购物项的数量+1
                cartItem.setQuantity(cartItem.getQuantity() + 1);
            }
        }
    
        //购物车的总价就是所有购物项的价格加起来
        public double getPrice() {
    
            double totalPrice = 0;
    
            for (Map.Entry<String, CartItem> me : bookMap.entrySet()) {
    
                //得到每个购物项
                CartItem cartItem = me.getValue();
    
                //将每个购物项的钱加起来，就是购物车的总价了！
                totalPrice += cartItem.getPrice();
            }
    
            return totalPrice;
        }
    
    
        public Map<String, CartItem> getBookMap() {
            return bookMap;
        }
    
        public void setBookMap(Map<String, CartItem> bookMap) {
            this.bookMap = bookMap;
        }
    
    
        public void setPrice(double price) {
            this.price = price;
        }
    }