#JAVA INTERFACE DEFAULT METHODS CODE#

i.e., third-party vendors need to implement it fullyĬonsider using the interface when our problem makes the statement “A is capable of ”. When application functionalities have to be defined as a contract, but not concerned about who implements the behavior.For example, Comparable provides the compareTo() method that can be overridden to compare two objects When unrelated classes implement our interface.If the problem needs to be solved using multiple inheritances and is composed of different class hierarchies.Let’s look at some scenarios when one should go with an interface: You can however provide an extension method on the interface if. While in abstract classes, we can never have this restriction on the number of abstract methods declaration. I suspect the reason is that you cant do that in Java. We can use this feature to restrict the number of abstract methods to be declared. In Scala, methods inside traits are quite useful. default methods in interfaces were added in Java 8, essentially to support the use of lambdas inside collections without breaking retro-compatibility with previous versions of the language. Any interface with a single abstract method other than static and default methods is considered a functional interface. Java 9 is near to come and more features will be added to Java interfaces, like private methods.

Java 8 introduced functional interfaces, an interface with a restriction of no more than one declared abstract method. Based on the requirement implementation class can use these default methods. Abstract classes may also have constructors which will get executed during the child object’s instantiation. Interface default methods are by default available to all implementation classes. In particular, default methods enable you to add methods that accept lambda expressions as parameters to existing interfaces.

#JAVA INTERFACE DEFAULT METHODS CODE#

We can have instance and static initialization blocks in an abstract class, whereas we can never have them in the interface. Default methods enable you to add new functionality to existing interfaces and ensure binary compatibility with code written for older versions of those interfaces.

Suppose if a class has a method that is abstract, then the class itself must be abstract.Ībstract classes have no restrictions on field and method modifiers, while in an interface, all are public by default. Default method or Defender method is one of the newly added features in Java 8. It also allows us to declare method signatures using the abstract keyword (abstract method) and forces its subclasses to implement all the declared methods. An abstract class is nothing but a class that is declared using the abstract keyword.

Java interface default methods