Relationship between class and interface

Difference between a class and an interface in Java | Java67

relationship between class and interface

package relationships; class Car { // Methods implementation and the interface of a front-end class without affecting back-end classes. An interface has fully abstract methods i.e. methods with nobody. An interface is syntactically similar to the class but there is a major difference between class. There is no relationship between the objects which implement same interface. Both are independent implementations of their own. They just follow the protocol .

For example, an airplane is made up of a fuselage, wings, engines, landing gear, flaps, and so on. A delivery shipment contains one or more packages. A team consists of two or more employees. These are all examples of the concept of aggregation, which represents "is part of" relationships. An engine is part of a plane, a package is part of a shipment, and an employee is part of a team.

Aggregation is a specialization of association, specifying a whole-part relationship between two objects. Composition is a stronger form of aggregation where the whole and parts have coincident lifetimes, and it is very common for the whole to manage the lifecycle of its parts.

IS-A between class and interface (OCPJP forum at Coderanch)

From a stylistic point of view, because aggregation and composition are both specializations of association the guidelines for associations apply. The members of an interface are always public. Methods The methods of a class are defined to perform a specific action. The methods in an interface are purely abstract.

relationship between class and interface

An interface can extend multiple interfaces but can not implement any interface. Constructor A class can have constructors to initialize the variables.

java - Relationships between classes that implement same interface - Stack Overflow

An interface can never have a constructor as there is hardly any variable to initialize. A class creates reference types and these reference types are used to create objects. A class has a signature and a body. The body of a class has fields and methods that operate on those fields.

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A Class is created using a keyword class. Lets us see how to declare a class. The fields and members declared inside a class can be static or nonstatic. Static members value is constant for each object whereas, the non-static members are initialized by each object differently according to its requirement.

Members of a class have access specifiers that decide the visibility and accessibility of the members to the user or to the subclasses. The access specifiers are public, private and protected. A class can be inherited by an another class using the access specifier which will decide the visibility of members of a superclass inherited class in a subclass inheriting class.

relationship between class and interface

The points I have discussed there, also applicable here in terms of rules of Java programming related to class and interface. Difference between class and interface in Java Now, let's examine both syntactical and functional difference between a class and interface in Java point by point, this will give you a better idea of both of them.

It is even recommended by Joshua Bloch in Effective Java. Since an interface can extend multiple interfaces and a class can implement multiple interfaces, it suddenly becomes more polymorphic.

On the other hand, a class is best suited for writing concrete code which does the actual job. You cannot define state variable inside interface in Java until JDK 7 but that is changed now in Java SE 8, where you can define both static and default methods inside interface. Horstmann to learn more about static and default methods 4 Inheritance A class can only inherit one class but an interface can extend multiple interfaces.

Difference Between Class and Interface in Java

Similarly, a class can implement multiple interfaces but an interface cannot extend a class. Any code which is written using interface are more adaptable to a change than code written using concrete classes. This is also a popular object oriented design principle, commonly known as "programming for interfaces than implementation".