[Java知识库]Java流中的MAP操作

Map是流中的一个中间操作。返回流。地图法java.util.stream.Stream类接受函数类型的参数，下面的代码计算流中图书的总价。

在BookStoreFacade类的getTotalPrice方法中使用map操作返回价格流。Map方法返回Stream。然后在Stream上调用forEach方法来获取所有书籍的价格之和。

class Book {
    private String publisher;
    private String author;
    private String name;
    private float price;

    public Book(String name, String author, float price, 
            String publisher) {
	this.name = name;
	this.author = author;
	this.price = price;
	this.publisher = publisher; 
    }

    /* Getter-Setter methods for each property */

    public float getPrice() {
        return price;
    }

    public String toString() {
	return "Title: " + name 
	    + ", Author: " + author 
	    + ", Price: " + price 
	    + ", Publisher: " + publisher;
    }
}

class BookStoreFacade {
    private float totalPrice;

    public float getTotalPrice(Stream<Book> bookStream) {
 	totalPrice = 0;
    <strong>    bookStream.map(b -> b.getPrice())</strong>
            <strong>.forEach(price -> totalPrice += price);
</strong>	return totalPrice;
    }
}

class Main {
    public static void main(String args[]) {
	List<Book> books = new ArrayList<>();
	books.add(new Book("You can win", "Shiv Khera", 75, 
            "Bloomsbury Publishing"));
	books.add(new Book("Indian Ethics", "Shyam Ranganathan", 
            2807, "Bloomsbury Publishing"));
	BookStoreFacade bookstore =new BookStoreFacade();
	System.out.println("Total Price : " 
            + bookstore.getTotalPrice(books.stream()));

    }
}

代码1.流中地图操作的使用