Mastering Core Java Concepts

What are the four main principles of Object-Oriented Programming?

• Encapsulation, Abstraction, Inheritance, Polymorphism

• Polymorphism, Data Abstraction, Class, Object

• Composition, Aggregation, Delegation, Interface

• Inheritance, Composition, Encapsulation, Data Hiding

Explain the concept of inheritance in Java.

• Inheritance is a method of data encryption in Java.

• Inheritance allows a class to create multiple instances of itself.

• Inheritance in Java is used to define interfaces only.

• Inheritance in Java allows a class to inherit properties and behaviors (methods) from another class, promoting code reuse and establishing a parent-child relationship between classes.

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 only relevant for primitive data types in Java.

• Encapsulation allows unrestricted access to all class components.

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

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

• An abstract class can have implemented methods and state, while an interface cannot.

• An abstract class is always public, while an interface is always private.

• An interface can have state and implemented methods.

• An abstract class cannot have any methods.

How does Java handle exceptions?

• Java uses try-catch-finally blocks to handle exceptions.

• Java does not support exception handling.

• Java requires all exceptions to be handled at compile time.

• Java uses only if-else statements for error handling.

What is the purpose of the try-catch block in Java?

• To improve code readability.

• To define variables in a method.

• To handle exceptions and prevent program crashes.

• To optimize memory usage.

Explain the difference between checked and unchecked exceptions.

• Both checked and unchecked exceptions require handling.

• Checked exceptions require handling or declaration, while unchecked exceptions do not.

• Checked exceptions are always runtime errors.

• Unchecked exceptions must be declared in the method signature.

What is the finally block used for in exception handling?

• The finally block is only executed if an exception occurs.

• The finally block ensures that specific code runs after try and catch blocks, regardless of exceptions.

• The finally block is used to define a new exception type.

• The finally block is used to catch exceptions before they are thrown.

What is the Java Collections Framework?

• A library for network programming in Java.

• A unified architecture for representing and manipulating collections of objects in Java.

• A set of tools for database management in Java.

• A framework for building graphical user interfaces in Java.