MainComparator.java

package examples;

import java.util.function.Function;

public class MainComparator {

    public static void main(String[] args) {
        
        Comparator<Person> cmpAge = (p1, p2) -> p2.getAge() - p1.getAge(); 
        Comparator<Person> cmpFirstName = (p1, p2) -> p1.getFirstName().compareTo(p2.getFirstName()); 
        Comparator<Person> cmpLastName = (p1, p2) -> p1.getLastName().compareTo(p2.getLastName());
    
        Function<Person, Integer> f1 = p -> p.getAge();
        Function<Person, String> f2 = p -> p.getFirstName();
        Function<Person, String> f3 = p -> p.getLastName();

        //Comparator<Person> cmpPerson = Comparator.comparing(f1);

        Comparator<Person> cmpPersonAge = Comparator.comparing(Person::getAge);
        Comparator<Person> cmpPersonFirstName = Comparator.comparing(Person::getFirstName);

        
        Comparator<Person> cmp = Comparator.comparing(Person::getFirstName)
                                            .thenComparing(Person::getFirstName)
                                            .thenComparing(Person::getAge);

    }

}