JAVA INTERFACE CODE

Otherwise, the design will just break down so default interface methods are an efficient way to deal with this issue. In a typical design based on abstractions, where an interface has one or multiple implementations, if one or more methods are added to the interface, all the implementations will be forced to implement them too.

JAVA INTERFACE CODE

Default methods enable you to add new functionality to the interfaces of your libraries and ensure binary compatibility with code written for older versions of those interfaces.

Default Method in Interface Why Default Methods in Interfaces Are Needed

Implementation for all of the inherited abstract methods. The first concrete class that implements an interface, or extends anĪbstract class that implements an interface, must provide an There are two inheritance rules you should keep in mind when extending an interface 1.Īn interface that extends another interface, as well as an abstractĬlass that implements an interface, inherits all of the abstract methods Therefore, marking a method as private, protected, or final will trigger compiler errors as these are incompatible with the abstract and public keywords. All non default methods in an interface are assumed to have the modifiers abstract and public in their definition. Therefore, marking an interface as private, protected, or final will trigger a compiler error, since this is incompatible with these assumptions.ĥ. An interface may not be marked as final.Īll top-level interfaces are assumed to have public or default access,Īnd they must include the abstract modifier in their definition. An interface is not required to have any methods.ģ. Interfaces cannot be instantiated directly.Ģ. You should recognize as adaptions of the rules for defining abstractġ. Java 8 brought to the table a few brand new features, including lambda expressions, functional interfaces, method references, streams, Optional, and static and default methods in interfaces.įollowing is a list of rules for creating an interface, many of which

are just contracts or signatures and they don't know anything about implementations. defining a method to measure current speed Since the Java class can implement multiple interfaces, it’s better to use interfaces as the superclass in most cases.Interfaces are suitable starting points to define Type and create a top-level hierarchy in our code.The interface provides a contract for all the implementation classes, so it’s good to code in terms of interfaces because implementation classes can’t remove the methods we are using.Outer.Welcome welcome=new NestedInt2() //upcasting See the below code example of Java Interface Inheritance. Here also extends keyword is used to extend the interface. One class extends another class in the same way one interface can extend another interface. In the above case, drive() is an abstract method in an interface car, and it is defined in a Tesla class. Therefore, whenever any class implements an interface, we must define every interface method otherwise, the class will turn into an abstract class. Methods in an interface are, by default, an abstract method. First, it has to provide the body of all the methods declared in an interface in other words, the class must implement all the interface methods. This is how a class implements an interface. ('Implementing interface firstInterface') See the following example of the Ip.java file. Syntax of Java Interface interface Interface_name However, we must use the “interface” keyword instead of class.

In Interface, only one specifier is used- Public. The access specifiers used with classes are private, protected, and public. The interface cannot contain concrete(with implementation) methods. In an interface, you can’t instantiate variables and create an object.Ĭlass can contain concrete(with implementation) methods.

In class, you can instantiate the variable and create an object. The class cannot implement two Java interfaces with methods with the same name but different return types.ĭifference between Class and Interface Class.Otherwise, the compiler will throw an error. At the time of declaration, the interface variable must be initialized.An interface declared inside another interface is referred to as a nested interface.It has to extend another interface if needed. An interface cannot implement another Interface.Whenever a class wants to implement any interface, that class needs to use the “implements” keyword instead of “extends.”.The interface does not have a constructor.We cannot create an object for an interface, i.e., not instantiated.The data types are public, static, and final in an Interface.It has methods, and by default, they are abstract.