Understanding Object-Oriented Java

What is the main principle of Object-Oriented Programming?

• Data structures, algorithms, and functions.

• Modularity, concurrency, and security.

• Static typing, dynamic binding, and recursion.

• Encapsulation, inheritance, polymorphism, and abstraction.

Explain the concept of inheritance in Java.

• Inheritance allows a subclass to inherit properties and behaviors from a superclass, promoting code reuse and establishing a hierarchical relationship.

• Inheritance is a way to hide properties and methods from subclasses.

• Inheritance is a method for creating new classes without any relationship to existing ones.

• Inheritance allows a superclass to inherit properties from a subclass.

What is polymorphism and how is it implemented in Java?

• Polymorphism is only achieved through inheritance in Java.

• Polymorphism is a feature exclusive to C++ and not applicable in Java.

• Polymorphism can only be implemented using abstract classes in Java.

• Polymorphism in Java is implemented through method overriding and interfaces.

Define encapsulation and its importance in Java.

• Encapsulation is the practice of bundling the data (attributes) and methods (functions) that operate on the data into a single unit or class, while restricting access to some of the object's components.

• Encapsulation is the process of separating data from methods in Java.

• Encapsulation is only relevant for primitive data types in Java.

• Encapsulation allows unrestricted access to all class components.

What is an interface in Java and how does it differ from an abstract class?

• An interface can only contain static methods, while an abstract class can contain instance methods.

• An abstract class can be instantiated, but an interface cannot.

• An interface is a contract that classes can implement, while an abstract class can provide some method implementations and state.

• An interface can have instance variables, while an abstract class cannot.

How do constructors work in Java?

• Constructors in Java initialize objects and have the same name as the class.

• Constructors are optional and not required for object creation.

• Constructors are used to destroy objects in Java.

• Constructors can have different names than the class.

What is the purpose of the 'this' keyword in Java?

• The 'this' keyword is used to create new classes in Java.

• The 'this' keyword is used to define static methods in Java.

• The 'this' keyword is used to refer to the current object instance in Java.

• The 'this' keyword is used to access global variables in Java.

Can you explain method overloading and method overriding in Java?

• Method overloading is when multiple methods have the same name with different parameters; method overriding is when a subclass redefines a method from its superclass.

• Method overloading requires different method names; method overriding cannot change the method signature.

• Method overloading is only possible in the same class; method overriding is not allowed in subclasses.

• Method overloading and overriding are the same concept in Java.