Given the code fragments:
public class Book implements Comparator
String name;
double price;
public Book () {}
public Book(String name, double price) {
this.name = name;
this.price = price;
}
public int compare(Book b1, Book b2) {
return b1.name.compareTo(b2.name);
}
public String toString() {
return name + ":" + price;
}
}
and
List
new Book ("Beginning with Java", 2),
new book ("A Guide to Java Tour", 3)
);
Collections.sort(books, new Book());
System.out.print(books);
What is the result?
The given code defines a class Book that implements Comparator<Book>. The compare method in the Book class compares two Book objects based on their names in ascending order. The code snippet then creates a list of Book objects and sorts them using the compare method, resulting in the list being sorted by book titles. Hence, the correct output will be [A Guide to Java Tour:3.0, Beginning with Java:2.0].
A is correct
A,tested
If we change places to that return b2.name.compareTo(b1.name) answer is B.
Correct answer is A but my question is on the exam which answer to choose? cause it might happen that the system is programmed to select D as the correct answer even if you choose A you become incorrect? class Testing implements Comparator<Testing> { String name; double price; public Testing () {} public Testing(String name, double price) { this.name = name; this.price = price; } public int compare(Testing b1, Testing b2) { return b1.name.compareTo(b2.name); } public String toString() { return name + ":" + price; } public static void main (String[] args){ List<Testing>books = Arrays.asList ( new Testing ("Beginning with Java", 2), new Testing ("A Guide to Java Tour", 3) ); Collections.sort(books, new Testing()); System.out.print(books); } }
The correct answer is A. Tested import java.util.Arrays; import java.util.Collections; import java.util.Comparator; import java.util.List; class Book implements Comparator<Book> { String name; double price; public Book () {} public Book(String name, double price) { this.name = name; this.price = price; } public int compare(Book b1, Book b2) { return b1.name.compareTo(b2.name); } public String toString() { return name + ":" + price; } } public class CollectionsSortBook { public static void main(String[] args) { List<Book> books = Arrays.asList ( new Book ("Beginning with Java", 2), new Book ("A Guide to Java Tour", 3) ); Collections.sort(books, new Book()); System.out.print(books); } }
A is correct import java.util.Arrays; import java.util.Collections; import java.util.Comparator; import java.util.List; public class Book implements Comparator<Book> { String name; double price; public Book() { } public Book(String name, double price) { this.name = name; this.price = price; } public int compare(Book b1, Book b2) { return b1.name.compareTo(b2.name); } public String toString() { return name + ":" + price; } public static void main(String[] args) { List<Book> books = Arrays.asList( new Book("Beginning with Java", 2), new Book("A Guide to Java Tour", 3) ); Collections.sort(books, new Book()); System.out.print(books); } }
Answer is A as b1.name.compare(b2.name) sorts elements by name in ascending order.
Correct answer is A.