Java Programming Concepts

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

• Composition, Aggregation, Delegation, Interface

• Polymorphism, Abstraction, Data Binding, Event Handling

• Inheritance, Composition, Encapsulation, Serialization

• Encapsulation, Abstraction, Inheritance, Polymorphism

Explain the concept of inheritance in Java.

• Inheritance in Java restricts access to methods and properties of a class.

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

• Inheritance in Java is a way to define interfaces without implementation.

• Inheritance in Java allows a subclass to inherit properties and methods from a superclass, promoting code reusability and establishing a class hierarchy.

What is polymorphism and how is it implemented in Java?

• Polymorphism in Java is only achieved through inheritance.

• Polymorphism is a feature that allows multiple classes to have the same name.

• 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 a method for optimizing performance in Java applications.

• Encapsulation is the practice of restricting access to an object's data and methods, enhancing data protection and modularity in Java.

• Encapsulation is the process of combining multiple classes into one.

• Encapsulation allows all data to be public and accessible in Java.

What is the Java Collections Framework?

• A set of tools for Java GUI development

• The Java Collections Framework is a set of classes and interfaces that implement commonly reusable collection data structures.

• A framework for building Java applications

• A library for Java networking functions

List three types of collections in Java and their use cases.

• Tree: Used for hierarchical data representation.

• Stack: Used for storing elements in a last-in-first-out order.

• 1. List: Used for ordered collections that allow duplicates. 2. Set: Used for collections of unique elements. 3. Map: Used for key-value pairs for fast lookups.

• Queue: Used for storing elements in a first-in-first-out order.

How do you convert an ArrayList to an array in Java?

• arrayList.toArray(new Type[arrayList.size()])

• arrayList.toArray(Type[])

• arrayList.toArray()

• arrayList.convertToArray()

What is the difference between List and Set in Java?

• List is a type of Set; Set is a type of List.

• List and Set are the same in Java, both allow duplicates and maintain order.

• List allows duplicates and maintains order; Set does not allow duplicates and is unordered.

• List does not allow duplicates and is unordered; Set allows duplicates and maintains order.

What is exception handling in Java?

• Exception handling in Java is a way to manage user input errors.

• Exception handling in Java is a mechanism to handle runtime errors using try, catch, and finally blocks.

• Exception handling in Java is used to improve program performance.

• Exception handling in Java is a method to optimize memory usage.

How do you create a custom exception in Java?

• public class MyCustomException extends RuntimeException { public MyCustomException(String message) {} }

• public class MyCustomException implements Exception {}

• public class MyCustomException { public MyCustomException() {} }

• public class MyCustomException extends Exception { public MyCustomException() {} public MyCustomException(String message) { super(message); } public MyCustomException(String message, Throwable cause) { super(message, cause); }}