Java8-Methodenreferenz

Lassen Sie uns diesmal die Java 8-Methodenreferenz mit Ihnen studieren.

Lassen Sie uns zunächst eine Methode für das Altersschwert nach der Methode vor Java 8 erstellen.

benutze lombok

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.*;

public class App {
    public static void main( String[] args ) {
        List<Person> personList = new ArrayList<Person>();
        personList.add(new Person("Jack",25));
        personList.add(new Person("Mary",23));
        personList.add(new Person("Jill",24));
        personList.add(new Person("Dock",34));
        personList.add(new Person("Lily",27));


        //Anonyme Klasse
        Collections.sort(personList, new Comparator<Person>() {
            @Override
            public int compare(Person o1, Person o2) {
                return o1.getAge() - o2.getAge();
            }
        });

        System.out.println(personList);
    }
}

@Data
@AllArgsConstructor
@NoArgsConstructor
class Person {
    private String name;
    private int age;
}

Implementierungsergebnis: [Person (Name = Mary, Alter = 23), Person (Name = Jill, Alter = 24), Person (Name = Jack, Alter = 25), Person (Name = Lily, Alter = 27), Person (Name = Dock, Alter = 34)]

Lambda-Formel

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.*;

public class App {
    public static void main( String[] args ) {
        List<Person> personList = new ArrayList<Person>();
        personList.add(new Person("Jack",25));
        personList.add(new Person("Mary",23));
        personList.add(new Person("Jill",24));
        personList.add(new Person("Dock",34));
        personList.add(new Person("Lily",27));

        //Lambda-Formel
        Collections.sort(personList,(p1,p2) -> p1.getAge() - p2.getAge());
        System.out.println(personList);
    }
}

@Data
@AllArgsConstructor
@NoArgsConstructor
class Person {
    private String name;
    private int age;
    
}

Implementierungsergebnis: [Person (Name = Mary, Alter = 23), Person (Name = Jill, Alter = 24), Person (Name = Jack, Alter = 25), Person (Name = Lily, Alter = 27), Person (Name = Dock, Alter = 34)]

statische Methodenreferenz

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.*;

public class App {
    public static void main( String[] args ) {
        List<Person> personList = new ArrayList<Person>();
        personList.add(new Person("Jack",25));
        personList.add(new Person("Mary",23));
        personList.add(new Person("Jill",24));
        personList.add(new Person("Dock",34));
        personList.add(new Person("Lily",27));

        //statische Methodenreferenz
        Collections.sort(personList, Person::CompareAge);
        System.out.println(personList);

    }
}

@Data
@AllArgsConstructor
@NoArgsConstructor
class Person {
    private String name;
    private int age;

    public static int CompareAge(Person o1, Person o2) {
        return o1.getAge() - o2.getAge();
    }
}