Java Reference
In-Depth Information
TRY IT OUT: Sorting an Array Using a Comparator
You can borrow the version of the Person class that implements the Comparable<> interface from the
TryVector example in Chapter 14 for this example. Copy the file to the directory you set
up for this example. The comparator needs access to the first name and the surname for a Person object
to make comparisons, so you need to add methods to the Person class to allow that:
public class Person implements Comparable<Person> {
public String getFirstName() {
return firstName;
public String getSurname() {
return surname;
// Rest of the class as before...
Directory "TrySortingWithComparator"
You can now define a class for a comparator that applies to Person objects:
import java.util.Comparator;
public class ComparePersons implements Comparator<Person> {
// Method to compare Person objects - order is descending
public int compare(Person person1, Person person2) {
int result =
return result == 0 ?
-person1.getFirstName().compareTo(person2.getFirstName()) :
// Method to compare with another comparator
public boolean equals(Object comparator) {
if(this == comparator) {
// If argument is the same
return true;
// then it must be equal
if(comparator == null) {
// If argument is null
return false;
// then it can't be equal
// Class must be the same for equal
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