Java Interview Question (Basic)

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.