Core JAVA Unit 1

Questions and Answers

What does WORA stand for in the context of Java?

Write Once, Run Anytime

Write Once, Reload Anywhere

Write Once, Run Anywhere (correct)

Write Once, Read Anywhere

Who developed the Java programming language?

Linus Torvalds

James Gosling (correct)

Guido van Rossum

Bjarne Stroustrup

Which of the following best describes the purpose of the Java Virtual Machine (JVM)?

It serves as a documentation tool for Java.

It manages the installation of Java on the system.

It compiles Java code into bytecode.

It executes Java bytecode on any supported platform. (correct)

Which feature of Java allows developers to create reusable code?

Modular programming Signup and view all the answers

What phase comes after the writing phase in the execution of a Java program?

Compilation phase Signup and view all the answers

What is the maxSpeed value of the base class Vehicle?

120 Signup and view all the answers

In the class hierarchy, how can the derived class Car access the maxSpeed of the base class Vehicle?

By using the super keyword Signup and view all the answers

What will be the output when the display method of the Car class is called?

Maximum Speed: 120 Signup and view all the answers

When is it necessary to use the super keyword with methods in a subclass?

When both classes have methods with the same name Signup and view all the answers

What does the message method in the Person class output?

This is person class Signup and view all the answers

Study Notes

Introduction to Java

Java is a class-based, object-oriented programming language.
It follows the "write once, run anywhere" (WORA) principle, allowing Java code to run on any platform that supports Java without recompilation.
Developed by James Gosling at Sun Microsystems in 1995, Java was later acquired by Oracle Corporation.
Known for simplicity, robustness, and security, making it popular for enterprise applications.
Java applications are compiled into bytecode for execution on any Java Virtual Machine (JVM).
The syntax of Java resembles C/C++, facilitating easier learning for those familiar with these languages.

Java Terminology

Java Virtual Machine (JVM): Executes bytecode generated by the JAVAC compiler during runtime.
JAVAC Compiler: Converts Java source code into bytecode, part of the Java Development Kit (JDK).

Use of `super` Keyword

Enables access to base class (parent class) members when both parent and child classes share the same data members, minimizing ambiguity.
Utilized to call methods in the parent class when there are overlapping method names between parent and child classes.
Supports polymorphism, allows subclasses to override methods and access parent class fields, providing a mechanism for code reuse and behavior customization.
Promotes abstraction and encapsulation, letting subclasses focus on their specific behaviors while relying on parent classes for implementation details.

Polymorphism

A key characteristic of Object-Oriented Programming, allowing one interface to have multiple implementations.
It is divided into two types:
- Compile-time Polymorphism (Static): Achieved through method overloading, allowing multiple methods with the same name but different parameters.
- Runtime Polymorphism (Dynamic): Achieved through method overriding, resolved at runtime, enabling method calls to adapted versions based on the object type.

Advantages of Polymorphism

Enhances code reusability by treating objects of different classes as objects of a common base class.
Supports method overloading and overriding, fostering flexible code design.

Encapsulation

Mechanism of wrapping data (variables) and methods into a single unit (class), restricting outside access to internal data.
Achieved by declaring instance variables as private and using public getters and setters for access and modification.
Protects data consistency and enforces validation rules, preventing unintended interference with the internal state.
Acts as a protective shield that limits external access to sensitive information.

Example Classes

Demonstrations of class inheritance, method overriding, and how the super keyword operates within the context of derived classes.
Vehicle and Car classes demonstrate variable shadowing and access using super.
Person and Student classes illustrate method overriding, differentiating behaviors between base and derived classes while employing the super keyword for parent method calls.

Description

This quiz covers Unit 1 of Core Java, focusing on the introduction to the Java programming language. It emphasizes Java's class-based and object-oriented nature, as well as its principle of 'write once, run anywhere'. Ideal for students beginning their journey in Java programming.