Java Reference
In-Depth Information
import java.io.Serializable;
class BookEntry implements Comparable<BookEntry>, Serializable {
public int compareTo(BookEntry entry) {
return person.compareTo(entry.getPerson());
}
// Rest of the class as before...
}
Directory "TryPhoneBook 2"
When sorting the entries, you want the sort order of the
Person
objects to determine the sort order of the
BookEntry
objects. Because the
Person
class already implements the
Comparable<>
interface, you can
implement the
compareTo()
method in the
BookEntry
class by calling the method for the
Person
object
in the entry.
Now you can implement the
listEntries()
method in the
PhoneBook
class to list the entries in alpha-
betical order:
import java.nio.file.*;
import java.io.*;
import java.util.*;
class PhoneBook implements Serializable {
// List all entries in the topic
public void listEntries() {
// Get the entries as a linked list
LinkedList<BookEntry> entries = new
LinkedList<>(phonebook.values());
Collections.sort(entries);
// Sort the entries
for(BookEntry entry : entries) {
System.out.println(entry);
}
}
// Other members as before...
}
Directory "TryPhoneBook 2"
Listing the entries in name sequence is relatively simple. Calling the
values()
method for the phone-
book object returns the objects in the map, which are
BookEntry
objects, as a
Collection<>
. You
pass this to the constructor for the
LinkedList<BookEntry>
class to obtain a list of entries. The
LinkedList<>
class implements the
List<>
interface, so you can pass the
entries
object to the
sort()
