Asked by: Fabien Chabner
technology and computing programming languages

How do has a relationships differ from is a relationships?

Last Updated: 28th February, 2020

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In Java, a Has-A relationship is also known as composition. In Java, a Has-A relationship simply means that an instance of one class has a reference to an instance of another class or an other instance of the same class. For example, a car has an engine, a dog has a tail and so on.

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Similarly, it is asked, is a Versus has a relationships?

Wherever you see an extends keyword or implements keyword in a class declaration, then this class is said to have IS-A relationship. HAS-A Relationship: Composition(HAS-A) simply mean the use of instance variables that are references to other objects. For example Maruti has Engine, or House has Bathroom.

One may also ask, what is an is a relationship between a class and an interface? When a class implements an interface, the class agrees to implement all of the methods defined in the interface. The important line is the bottom, there is no class relationship between classes that impliment an interface. You cant view it in the same way you would with instances of classes and abstract classes.

Similarly, why is composition called a has a relationship and inheritance called an is a relationship?

Inheritance (is-a) relationships are derived child classes that inherit attributes and methods from their parent class. Composition (has-a) relationships are classes whose attributes are comprised of other classes. Each relationship has its advantages and disadvantages.

Is a relationship example?

In Object oriented programming, IS-A relationship denotes “one object is type of another”. IS-A relation denotes Inheritance methodology. In Java, Inheritance can be implemented with extends (in case of class) and implements(in case of interface) keywords. A simple example of IS-A relation : Dell IS-A laptop.

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