A bookstore's sales are represented by a list of Sale objects populated with the name of the customer and the books they purchased. public class Sale { String customer; private List items; /* constructor, setters and getters not shown */ } public class Book { private String name; private double price; /* constructor, setters and getters not shown */ } Given a list of Sale objects, lList, which code fragment creates a list of total sales for each customer in ascending order?

Question

A bookstore's sales are represented by a list of Sale objects populated with the name of the customer and the books they purchased.

public class Sale {
 String customer;
 private List<Book> items;
 /* constructor, setters and getters not shown */
}

public class Book {
 private String name;
 private double price;
 /* constructor, setters and getters not shown */
}

Given a list of Sale objects, lList, which code fragment creates a list of total sales for each customer in ascending order?

Accepted Answer

C. lList.stream()
 .collect(groupingBy(Sale::getCustomer, 
 summingDouble(sale -> sale.getItems().stream().mapToDouble(Book::getPrice).sum())));
 .entrySet().stream().sorted(Map.Entry.comparingByValue())
 .collect(mapping(Entry::getKey, toList()));

Answer

A. lList.stream()
 .collect(groupingBy(Sale::getCustomer, TreeMap::new, 
 summingDouble(sale -> sale.getItems().stream().mapToDouble(Book::getPrice).sum())));
 .entrySet().stream().sorted(Map.Entry.comparingByValue())
 .collect(mapping(Entry::getKey, toList()));

Answer

B. lList.stream()
 .collect(groupingBy(Sale::getCustomer, 
 summingDouble(sale -> sale.getItems().stream().mapToDouble(Book::getPrice).sum())));
 .entrySet().stream().sorted(Map.Entry.comparingByValue())
 .collect(mapping(Entry::getKey, toList()));

Answer

D. lList.stream()
 .collect(groupingBy(Sale::getCustomer, 
 summingDouble(sale -> sale.getItems().stream().mapToDouble(Book::getPrice).sum())));
 .entrySet().stream().sorted(Map.Entry.comparingByValue())
 .collect(mapping(Entry::getKey, toList()));

A bookstore's sales are represented by a list of Sale objects populated with the name of the customer and the books they purchased. public class Sale { String customer; private List<Book> items; /…

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