Java 8 Method-References

In java 8 new feature introduce method Reference.Method Reference is used to refer method of functional interface.

when we used Lambda expression to just referring a method.we can replace our lambda expression with method Reference.

Type of Method Referencess

1. Reference to static method. (Example :ContainingClass::staticMethodName)
2. Reference to instance method of particular object (Example :containingObject::instanceMethodName)
3. Reference to constructor (example :ClassName:: new)

1)Reference to static method:-

  Used to refer static methods from a class

          interface TestMethod{  

              void shop();  

          }  

          public class SampleExample{  

           public static void testReferance(){  

               System.out.println("Hello,world !");  

          }  

          public static void main(String[] args) {  

          TestMethod testMethod= SampleExample::testReferance; // Referring static method  

          testMethod.shop(); // Calling interface method    

    }  

} 

2) Reference to instance method of particular object

 In this type we are referring non-static methods. You can refer methods by class object and anonymous object.

interface TestMethod{  

    void say();  

}  

public class InstanceMethodRef {  

    public void testReferance(){  

        System.out.println("Hello, this is non-static method.");  

    }  

    public static void main(String[] args) {  

        InstanceMethodRef methodRef = new InstanceMethodRef();  

        TestMethod testMethod = methodRef::saySomething;  // Referring non-static method using reference   

            testMethod.shop();  // Calling interface method 

            // Referring non-static method using anonymous object  

            TestMethod sayable2 = new InstanceMethodRef()::testReferance;  

            // Calling interface method  

            testMethod2.shop();  

    }  

}  

3) Reference to a Constructor

 In this type , we are referring constructor with the help of functional interface.

interface TestMethod{  

    ConsMethod getMessage(String msg);  

}  

class ConsMethod{  

    Message(String msg){  

        System.out.print(msg);  

    }  

}  

public class ConstructorRef {  

    public static void main(String[] args) {  

        TestMethod hello = ConsMethod::new;  

        hello.getMessage("Hello world");  

    }  

}