Java Interview Question (Basic)
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Questions and Answers

Which class is preferable to use when creating strings from a single thread?

  • String
  • All three classes are equally preferable
  • String Builder (correct)
  • String Buffer

    • Why are strings immutable in Java?

  • To allow for easy comparison
  • To maintain thread safety
  • To save memory
  • To prevent changes to the value (correct)

    • What is the difference between the == operator and the .equals() method for comparing strings?

  • == compares references, .equals() compares memory locations
  • == compares values, .equals() compares memory locations
  • == compares memory locations, .equals() compares references
  • == compares memory locations, .equals() compares values (correct)

    • What is the purpose of abstraction in Java?

    <p>To hide implementation details</p> Signup and view all the answers

    Which type of inheritance involves multiple child classes inheriting properties from multiple parent classes?

    <p>Multi-level inheritance</p> Signup and view all the answers

    What is the term for creating and implementing a method with the same name in a subclass as the parent class?

    <p>Method overriding</p> Signup and view all the answers

    What is the term for a class that inherits properties or functions from another class?

    <p>Derived class</p> Signup and view all the answers

    Why does Java not support multiple inheritances?

    <p>To avoid the diamond problem</p> Signup and view all the answers

    Which keyword is used to point to the current instance of a method or a constructor?

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

    What is constructor chaining?

    <p>Calling one constructor of the class using another constructor of the same class</p> Signup and view all the answers

    What is the superclass of all the classes existing in Java?

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

    Why are pointers not supported in Java?

    <p>To achieve security by abstraction</p> Signup and view all the answers

    Which type of constructor is created by the compiler when no constructor is defined in the program?

    <p>Default constructor</p> Signup and view all the answers

    Can a constructor be overloaded?

    <p>Yes, a constructor can be overloaded.</p> Signup and view all the answers

    Can constructors be inherited?

    <p>No, a constructor cannot be inherited.</p> Signup and view all the answers

    What is the difference between constructors and methods?

    <p>Constructors are invoked when a class is instantiated, while methods are called to perform some action.</p> Signup and view all the answers

    Which one of these is true about the Java Runtime Environment (JRE)?

    <p>JRE is the platform that provides the environment for running Java programs.</p> Signup and view all the answers

    What is the role of the Java Virtual Machine (JVM)?

    <p>JVM verifies and executes the program line by line.</p> Signup and view all the answers

    Why is Java considered platform-independent?

    <p>Java code is compiled into an intermediate language called Bytecode.</p> Signup and view all the answers

    What is the role of the Just In Time (JIT) compiler?

    <p>JIT optimizes and runs the code in the least possible time.</p> Signup and view all the answers

    Which method can be declared final?

    <p>The main method</p> Signup and view all the answers

    Can an interface be declared as final?

    <p>An interface can never be final</p> Signup and view all the answers

    What is static binding?

    <p>Identifying classes and objects during compile time</p> Signup and view all the answers

    What is dynamic binding?

    <p>Identifying classes and objects during run time</p> Signup and view all the answers

    What does the InstanceOf operator do?

    <p>Checks if the object is an instance of a class or subclass</p> Signup and view all the answers

    What is a multithreaded program?

    <p>A program that executes multiple threads concurrently</p> Signup and view all the answers

    Ques.1. What is Java?

    <p>Java is an object-oriented programming language used to develop applications.</p> Signup and view all the answers

    Ques.2. What are some features of Java?

    <p>Java programs can perform various tasks simultaneously due to its multi-threaded feature.</p> Signup and view all the answers

    Ques.3. What is JDK?

    <p>JDK stands for Java Development Kit and provides an environment to build, run, and execute programs.</p> Signup and view all the answers

    Ques.4. What is Javac?

    <p>Javac is a compiler used in Java to convert the Java program code into bytecodes.</p> Signup and view all the answers

    Which method is used to toggle a checkbox in Selenium WebDriver?

    <p>click()</p> Signup and view all the answers

    How can you check if a checkbox is toggled on in Selenium WebDriver?

    <p>isSelected()</p> Signup and view all the answers

    In the given code, what is the purpose of 'driver.get()' method?

    <p>To navigate to a specific URL</p> Signup and view all the answers

    What is the purpose of the 'persist_box' element in the given code?

    <p>To represent a checkbox element</p> Signup and view all the answers

    What is the role of the 'System.out.println()' method in the given code?

    <p>To print a message to the console</p> Signup and view all the answers

    What is the purpose of the 'id("vfb-6-0")' expression in the given code?

    <p>To find an element by its ID</p> Signup and view all the answers

    What is the purpose of the 'WebElement' class in Selenium WebDriver?

    <p>To represent an HTML element</p> Signup and view all the answers

    What is the purpose of the 'for' loop in the given code?

    <p>To iterate over a range of values</p> Signup and view all the answers

    Which method is used to toggle on a radio button in Selenium?

    <p>click()</p> Signup and view all the answers

    What is the purpose of the isSelected() method in Selenium?

    <p>To check if a checkbox is selected</p> Signup and view all the answers

    Which method is used to toggle a checkbox on/off in Selenium?

    <p>click()</p> Signup and view all the answers

    What is the output of the code 'System.out.println("Radio Button Option 1 Selected");' when the 'Option1' radio button is selected?

    <p>Radio Button Option 1 Selected</p> Signup and view all the answers

    What is the output of the code 'System.out.println("Radio Button Option 2 Selected");' when the 'Option2' radio button is selected?

    <p>Radio Button Option 2 Selected</p> Signup and view all the answers

    What is the output of the code 'System.out.println("Radio Button Option 2 Selected");' when the 'Option1' radio button is selected?

    <p>Radio Button Option 2 Selected</p> Signup and view all the answers

    What is the output of the code 'System.out.println("Radio Button Option 1 Selected");' when the 'Option2' radio button is selected?

    <p>Radio Button Option 1 Selected</p> Signup and view all the answers

    What is the purpose of the code 'isSelected() method is used to know whether the Checkbox is toggled on or off.'?

    <p>To check if a checkbox is selected</p> Signup and view all the answers

    Study Notes

    Java Basics

    • String class is preferable to use when creating strings from a single thread.
    • Strings are immutable in Java because they cannot be changed once created.
    • == operator checks for reference equality, whereas .equals() method checks for content equality when comparing strings.

    OOP Concepts

    • Abstraction is a concept in Java that shows only the necessary information to the outside world while hiding the internal details.
    • Multiple inheritance involves multiple child classes inheriting properties from multiple parent classes, but Java does not support multiple inheritances.
    • Overriding is the term for creating and implementing a method with the same name in a subclass as the parent class.
    • Inheritance is the term for a class that inherits properties or functions from another class.
    • Java does not support multiple inheritances to avoid ambiguity and complexity.

    Constructors and Methods

    • this keyword is used to point to the current instance of a method or a constructor.
    • Constructor chaining is a process of calling one constructor from another constructor.
    • Object is the superclass of all the classes existing in Java.
    • Pointers are not supported in Java because they can lead to memory leaks and security risks.
    • Default constructor is a type of constructor that is created by the compiler when no constructor is defined in the program.
    • Constructors can be overloaded, but they cannot be inherited.
    • Constructors are used to initialize objects, whereas methods are used to perform actions.

    Java Runtime Environment (JRE)

    • JRE is responsible for providing the environment for Java programs to run.
    • Java Virtual Machine (JVM) is responsible for executing Java programs.
    • Java is considered platform-independent because it can run on any platform that has a JVM.
    • Just In Time (JIT) compiler is responsible for improving the performance of Java programs.

    Methods and Binding

    • final method can be declared final, which means it cannot be overridden.
    • An interface cannot be declared as final.
    • Static binding is a process of binding at compile-time, whereas dynamic binding is a process of binding at runtime.
    • InstanceOf operator is used to check if an object is an instance of a particular class.

    Multithreading

    • A multithreaded program is a program that can execute multiple threads concurrently.

    Selenium WebDriver

    • driver.get() method is used to navigate to a webpage.
    • persist_box element is used to store the checkbox state.
    • System.out.println() method is used to print output to the console.
    • id("vfb-6-0") expression is used to locate an element by its ID.
    • WebElement class is used to interact with web elements.
    • for loop is used to iterate over a collection of web elements.
    • isSelected() method is used to check if a checkbox is selected.
    • click() method is used to toggle a checkbox or radio button.

    Radio Buttons and Checkboxes

    • isSelected() method is used to check if a radio button is selected.
    • click() method is used to toggle a radio button or checkbox on/off.

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    Description

    Test your knowledge on Object-Oriented Programming (OOP) concepts with this quiz. Learn about the benefits of using OOP, such as code organization, reusability, and data hiding. Also, explore the concept of the super keyword and its significance in OOP. Challenge yourself and improve your understanding of OOP principles with this quiz.

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