Java 8 – Method Reference – Is it Magic?

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Amongst the notable features in Java8, Method Reference adds Shorthand syntax for a lambda expression. In most cases, Lambda expression does nothing more than just calling a single method. If you find yourself doing that most often, its time to look at Method reference. It can be used to replace entire Lambda expression, let’s have a look at following example

class Student {
  int rollNo;
  String name;
  LocalDate birthDate;

//Getter and setter goes here.

The Student class captures basic details like Roll Number, Birth Date and Student name. Let’s define a collection to store some student information

public class StudentApplication {
  public static void main(String[] args) {
    List students = new ArrayList<>();
    students.add(createStudent("Michael Freit", 122, LocalDate.of(1998, 05, 12)));
    students.add(createStudent("Jeremy Kahn", 110, LocalDate.of(1998, 01, 03)));
    students.add(createStudent("Hugo Patrick", 95, LocalDate.of(1998, 03, 24)));
    students.add(createStudent("Nathan Hendrige", 130, LocalDate.of(1998, 02, 18)));
    students.add(createStudent("Kate hudson", 117, LocalDate.of(1998, 04, 10)));

  private static Student createStudent(String name, int rollNo, LocalDate dateOfBirth) {
    Student student = new Student();
    return student;

What if you wish to simply print name of each student from the list. The pre-Java 8 syntax will be like

for(Student s : students){

Using Java 8, Lambda expression syntax will look like below -> student.getName()).forEach(s->System.out.println(s));

With Method expression, the code will look like;

Notice student -&gt; student.getName() is replaced with Student::getName and s-&gt;System.out.println(s) with System.out::println. In each of the Lambda expression, a single method was replaced with equivalent Method reference. Student::getName is a method reference of a defined type and System.out::println is an instance method of PrintStream object. In addition to that there are two more kinds.

  • Static method reference
  • Constructor reference

Static method reference
Static method reference requires a name of the class followed by the method name


Let’s understand it by writing some code.

public class Library {
  public static void main(String[] args) {
    List shelf = new ArrayList<>();
    shelf.add("Blockchain revolution");
    shelf.add("Start with WHY?");
    shelf.add("Flying without Net");

  private static void printBookName(String name) {

To print name of each book

Java 7 or before

for(String book : shelf) {

Java 8 with lambda -> printBookName(s));

With Java 8 method reference;

Constructor with new
This one is very easy, instead of using

new Integer();



So based on above examples Method Reference can be summarised as

Kind Pre-Java 8 Java 8
Static Method Class.staticMethod(); Class::staticMethod
Instance Method object.instanceMethod() object::instanceMethod
Instance Method of Specific Type sampleMethod(obj, args) { obj.callMe(args); } ObjectType::callMe
Constructor new SomeClass() SomeClass::new

That’s not all about Method Reference. Refer below example of how a thread can be created using a Method reference

public class ThreadDemo {
  public static void main(String[] args) {
    //Pre-Java 8
    Thread t = new Thread(new Runnable(){
      public void run(){

   Thread t2 = new Thread(()-> ThreadDemo.printName());

   //Java8-Method reference
   Thread t3 = new Thread(ThreadDemo::printName);

  private static void printName(){
    System.out.println("I am inside Thread!!!");

In next article, we will explore more about java.util.function package and identify how it fits with MethodReference and Lambda.

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