Double colon operator

Method and Constructor reference by using "::" operator

• The functional interface method can be mapped to our specified method by using "::" operator. This is called method reference.
• Our specified method can be either a static or instance method.
• The functional interface method and our specified method should have the same argument types except for return-type, method-name, modifiers, etc are not required to match.

Syntax
If our specified method is a static method.
Class-name::method-name

If the method is an instance method
Object-reference::method-name

Constructor references
We also can use ":: "operator to refer constructors
Syntax
Class-name::new

Example:

1. class Student{
2. private String name;
3. Student(String name){
4. this.name=name;
5. }
6. }
7. interface A{
8. public Student getName(String name);
9. }
10. class Test{
11. public static void main(String[] args){
12. A a= s-> new Sample(s);
13. a.getName("Anu");
14. A a1 = Student::new;
15. a1.getName("Kalawati");
16. }
17. }

Note: In method and constructor references compulsory the argument types must be matched.