Java Oop Interview Questions
Java OOP Interview Questions: Useful Tips and Examples
Java Oop Interview Questions
In Java OOP interview questions, candidates are typically asked about the four main principles of object-oriented programming: encapsulation, inheritance, polymorphism, and abstraction. They may also be asked to explain concepts such as method overloading, method overriding, access modifiers, and the difference between abstract classes and interfaces. Additionally, candidates may be quizzed on how they would design a class hierarchy for a specific scenario, or how they would implement specific design patterns in Java. It is important for candidates to demonstrate a solid understanding of object-oriented programming concepts and their practical application in Java programming.
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1 - What is OOP (Object Oriented Programming) and why is it important in Java?
OOP is a programming paradigm that allows you to model real world entities using objects, which contain data, in the form of fields or attributes, and code, in the form of methods. In Java, OOP is important because it promotes code reusability, modularity, and extensibility through concepts such as inheritance, encapsulation, and polymorphism.
2) What is the difference between abstraction and encapsulation in Java?
Abstraction is the concept of hiding the implementation details and showing only the essential features of an object. Encapsulation, on the other hand, is the mechanism that binds the data (attributes) and methods (behavior) into a single unit known as a class. Abstraction is achieved through interfaces and abstract classes, while encapsulation is achieved through access modifiers like private, protected, and public.
3) What is inheritance in Java and how does it promote code reusability?
Inheritance is the mechanism by which a new class, known as a subclass or derived class, can inherit attributes and methods from an existing class, known as a superclass or base class. This promotes code reusability by allowing the subclass to reuse the code implemented in the superclass without rewriting it.
4) What is the difference between method overloading and method overriding in Java?
Method overloading is when multiple methods with the same name but different parameters are defined within the same class. Method overriding, on the other hand, is when a method in a subclass has the same name, return type, and parameters as a method in its superclass. Method overloading is resolved at compile time, while method overriding is resolved at runtime.
5) What is polymorphism in Java and how is it achieved?
Polymorphism is the ability of an object to take many forms. In Java, polymorphism is achieved through method overriding, where a subclass can provide a specific implementation of a method defined in its superclass, and method overloading, where multiple methods with the same name but different signatures can coexist in the same class. This allows for flexibility and extensibility in the code.
6) How does the ‘super’ keyword work in Java?
The ‘super’ keyword in Java is used to refer to the superclass of the current object. It can be used to access superclass methods, constructor, and variables. By using ‘super’, you can differentiate between the superclass and subclass methods or variables with the same name, and also call the superclass constructor from the subclass constructor.
7) What is the difference between abstract classes and interfaces in Java?
Abstract classes can have both abstract (methods without implementation) and concrete methods, while interfaces can only have abstract methods (by default, all methods in interfaces are abstract). A class can implement multiple interfaces, but can only extend one abstract class. Abstract classes can have constructor and instance variables, while interfaces cannot have either.
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