JAVA TECHNICAL QUESTION AND ANSWERS FOR INTERVIEW PART IV INHERITANCE & INTERFACES

Summary

This video focuses on Java technical interview questions related to inheritance and interfaces. It explains key concepts like inheritance, including its types—single, multi-level, hierarchical, hybrid, and multiple inheritance—highlighting their differences and advantages. The discussion then moves to interfaces in Java, their purpose, and how they enable multiple inheritance. Additionally, it covers abstract classes, abstract methods, and the distinctions between abstract classes and interfaces. Method overriding is also explained, emphasizing its role in redefining superclass methods in a subclass. This comprehensive guide is ideal for those preparing for Java interviews.

Takeaways

• 💡 Inheritance in Java is the process of acquiring properties (instance variables) and behaviors (methods) from a superclass to a subclass, promoting reusability.
• 🔄 Java supports several types of inheritance: single inheritance, multi-level inheritance, hierarchical inheritance, hybrid inheritance, and multiple inheritance.
• 🔗 Single inheritance involves one superclass and one subclass, where the subclass inherits features from the superclass.
• 📚 Multi-level inheritance allows a subclass to inherit features from a derived class, forming a chain of inheritance (Class A -> Class B -> Class C).
• 📈 Hierarchical inheritance is when multiple classes inherit properties and behaviors from a single superclass.
• 🌀 Hybrid inheritance combines two or more types of inheritance, such as single, multi-level, or hierarchical inheritance.
• 🚫 Java doesn't support multiple inheritance directly but achieves it using interfaces. Multiple inheritance allows a subclass to inherit features from two or more superclasses.
• 🛠️ The `extends` keyword is used for inheritance in Java, while the `implements` keyword is used to implement interfaces.
• 🧩 An interface in Java is a collection of abstract methods and final variables, while an abstract class contains both abstract and concrete methods.
• 🔄 Method overriding in Java occurs when a subclass provides a specific implementation of a method already defined in its superclass, with the same name, return type, and parameters.

Q & A

What is inheritance in Java?

Inheritance in Java is the process where one class (subclass) acquires the properties (instance variables) and behavior (methods) from another class (superclass). The main advantage of inheritance is reusability, as the subclass can reuse existing code from the superclass.

What are the types of inheritance in Java?

The types of inheritance in Java are: single inheritance, multi-level inheritance, hierarchical inheritance, hybrid inheritance, and multiple inheritance.

What is single inheritance in Java?

Single inheritance is when a class (subclass) acquires properties and behavior from one superclass. For example, Class B inherits from Class A, where Class A is the superclass and Class B is the subclass.

What is multi-level inheritance in Java?

Multi-level inheritance occurs when a class (subclass) inherits properties and behavior from another derived class. For instance, Class C inherits from Class B, and Class B inherits from Class A, forming a chain of inheritance.

What is hierarchical inheritance in Java?

Hierarchical inheritance is when multiple subclasses acquire properties and behavior from a single superclass. For example, Class B and Class C both inherit from Class A.

What is hybrid inheritance in Java?

Hybrid inheritance is the combination of two or more types of inheritance, such as combining single and hierarchical inheritance.

What is multiple inheritance in Java, and how is it achieved?

Multiple inheritance is when a subclass acquires properties and behavior from two or more superclasses. In Java, this is achieved using interfaces, as Java does not support multiple inheritance with classes.

Which keyword is used to implement inheritance in Java?

The 'extends' keyword is used to implement inheritance in Java. A class can extend only one class at a time.

What is an interface in Java?

An interface in Java is a collection of abstract methods and final variables. Abstract methods are methods without a body definition.

What is the difference between an abstract class and an interface in Java?

An interface only contains abstract methods, whereas an abstract class can have both abstract and concrete methods (methods with a body definition).