4.14 Interface

Interface - To implement multiple inheritance in java we use interface

interface came to solve the diamond problem

• only definition of methods no implementations
• by default method will be public and abstract.
• Implement keyword will be use to inherit an interface
• it is must that the class which is implementing the interface have implementation of interface methods.

Interface types

1. Marker Interface - interface without any method

2. SAM - Single abstract method - in java 8 (Functional interface)

3. Normal interface

In java 8 

you can define and declare methods by using default or static keywords.

diamond problem again came when it is possible to implements methods in interface

interface I

{

default void show()

{

  System.out.println("Hello");

}

static void display()

 {

    System.out.println("Hi");

 }

 void work();

}

class interfaceTest implements I

{

public void work()

{

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

}

  public static void main(String args[])

 {

  interfaceTest obj=new interfaceTest();

  obj.work();

  I.display();

}

}