Core JAVA Unit 1
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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?

    <p>Modular programming</p> Signup and view all the answers

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

    <p>Compilation phase</p> Signup and view all the answers

    What is the maxSpeed value of the base class Vehicle?

    <p>120</p> Signup and view all the answers

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

    <p>By using the super keyword</p> Signup and view all the answers

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

    <p>Maximum Speed: 120</p> Signup and view all the answers

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

    <p>When both classes have methods with the same name</p> Signup and view all the answers

    What does the message method in the Person class output?

    <p>This is person class</p> 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.

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    Core Java UNIT 1.pdf

    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.

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