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#Java interface code#

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You want to specify the behavior of a particular data type but are not concerned about who implements its behavior.

A class can implement more than one interface.

It is a total abstraction, All methods declared within an interface must be implemented by the class(es) that implements this interface.

You can expect that the classes that extend an abstract class have many common methods or fields, or require access modifiers other than public (such as protected and private).Ĭonsider using interfaces if any of these statements apply to your situation:.

You can define the non-static or non-final field(s) in the abstract class so that via a method you can access and modify the state of the object to which they belong.

#Java interface code#

In the java application, there are some related classes that need to share some lines of code then you can put these lines of code within the abstract class and this abstract class should be extended by all these related classes.

A Java abstract class can have class members like private, protected, etc.Ĭonsider using abstract classes if any of these statements apply to your situation:

Accessibility of Data Members: Members of a Java interface are public by default.

Multiple Inheritance: Interface supports multiple inheritance an abstraction does not support multiple inheritance.

Multiple implementations: An interface can extend one or more Java interfaces an abstract class can extend another Java class and implement multiple Java interfaces.

Inheritance vs Abstraction: A Java interface can be implemented using the keyword “implements” and an abstract class can be extended using the keyword “extends”.

Interface can’t provide the implementation of an abstract class.

Implementation: Abstract class can provide the implementation of the interface.

The interface has only static and final variables.

Type of variables: Abstract class can have final, non-final, static and non-static variables.

An abstract class may contain non-final variables.

Final Variables: Variables declared in a Java interface are by default final.

From Java 9, it can have private concrete methods as well. From Java 8, it can have default and static methods also. An abstract class can have abstract and non-abstract methods.

Type of methods: Interface can have only abstract methods.

ISRO CS Syllabus for Scientist/Engineer Exam.

ISRO CS Original Papers and Official Keys.

GATE CS Original Papers and Official Keys.

These are the two main reference types in Java.Īn interface can contain a subset of what a normal class can contain. Testinterface1 obj = new testinterface1() Īn interface is a reference type, just like a class is. You would inherit from these classes almost exactly the same way: public class InheritsFromInterface To illustrate that point, look at the following code. I mentioned earlier that interfaces are just a special form of an abstract class. Likewise, z is of type interfaceB and there is no interfaceMethodA() in interfaceB. The reason you can't do this is that y is of type interfaceA, and there is no interfaceMethodB() in interfaceA. However, you could never do the following: public void testInterfaces() prints "interfaceB, interfaceMethodB, implementation B"

prints "interfaceA, interfaceMethodA, implementation B" prints "interfaceB, interfaceMethodB, implementation A" prints "interfaceA, interfaceMethodA, implementation A" ImplementingClassB v = new ImplementingClassB() ImplementingClassA u = new ImplementingClassA() Now if you wanted you could write a method like this: public void testInterfaces() ("interfaceB, interfaceMethodB, implementation B") ("interfaceA, interfaceMethodA, implementation B") ("interfaceB, interfaceMethodB, implementation A") ("interfaceA, interfaceMethodA, implementation A") Many classes can implement an interface, and a class can implement many interfaces: interface InterfaceA To use this interface, you simply need to implement the interface. So the interface above is identical to the interface below: public interface Interface Since the interface can't implement any methods, it's implied that the entire thing, including all the methods, are both public and abstract (abstract in Java terms means "not implemented by this class"). However, it can be achieved with interfaces, because the class can implement multiple interfaces. 2) Java does not support 'multiple inheritance' (a class can only inherit from one superclass). In Java, you create an interface like this: interface Interface 1) To achieve security - hide certain details and only show the important details of an object (interface). An interface is a special form of an abstract class which does not implement any methods.