Here’s a list of 20 core Java interview questions and answers that are relevant for Selenium automation testing:
- What is Java?
Java is a high-level, object-oriented programming language known for its platform independence and ability to run on various devices and operating systems.
- Explain Object-Oriented Programming (OOP) concepts.
OOP concepts include encapsulation, inheritance, abstraction, and polymorphism, which allow you to structure and organize code efficiently.
- What is the difference between int and Integer in Java?
int is a primitive data type, while Integer is a wrapper class for the int primitive type, allowing it to be used in object-oriented contexts.
- What is the significance of the static keyword?
static is used to define a class-level variable or method that belongs to the class rather than instances of the class. It can be accessed using the class name.
- Explain the final keyword.
The final keyword is used to make a variable, method, or class unchangeable or unextendable. A final variable cannot be reassigned, a final method cannot be overridden, and a final class cannot be extended.
- What is method overloading and method overriding?
Method overloading involves creating multiple methods in the same class with the same name but different parameters. Method overriding occurs when a subclass provides a specific implementation for a method defined in its superclass.
- What is the this keyword used for?
The ‘this’ keyword refers to the current instance of a class and can be used to differentiate between instance variables and method parameters with the same name.
- Explain the concept of exception handling in Java.
Exception handling is the process of dealing with runtime errors in a program. Java provides try, catch, finally, and throw keywords to manage exceptions.
- What is the difference between == and .equals() in Java?
== compares object references, while .equals() compares the content or values of objects.
- What is a constructor?
A constructor is a special method that is called when an object of a class is created. It initializes the object’s state.
- What is a package in Java?
A package is a collection of related classes and interfaces that are bundled together for organization and management.
- Explain the concept of method visibility (access modifiers).
Access modifiers (e.g., public, private, protected, package-private) define the level of visibility a class, method, or field has within the same class, package, or subclasses.
- What is the difference between ArrayList and LinkedList?
ArrayList is implemented as a dynamic array, while LinkedList is implemented as a doubly-linked list. ArrayList offers better performance for random access, while LinkedList is better for frequent insertions and deletions.
- How does garbage collection work in Java?
Garbage collection automatically reclaims memory used by objects that are no longer referenced by the program. The Java Virtual Machine (JVM) handles this process.
- What is the toString() method used for?
The toString() method is defined in the Object class and is used to provide a string representation of an object. It’s often overridden in custom classes to provide meaningful output.
- Explain the concept of interfaces in Java.
An interface defines a contract for a group of related methods that classes implementing the interface must provide. It enables multiple inheritance and is used for achieving abstraction.
- What is the super keyword used for?
The super keyword is used to access the methods and properties of the parent class (superclass) within a subclass.
- What is a static block?
A static block is a code block that’s executed when a class is loaded into memory. It’s used to initialize static variables or perform other one-time setup tasks.
- Explain the compareTo() method.
The compareTo() method is used to compare objects and is defined in the Comparable interface. It returns a negative value if the calling object is less than the argument, zero if they are equal, and a positive value if the calling object is greater.
- What are annotations in Java?
Annotations are metadata added to code to provide additional information to the compiler, runtime environment, or tools. In Selenium, annotations like @Test are used for test methods.
Remember to practice answering these questions and understanding the underlying concepts to perform well in your Java interview for Selenium automation testing roles.
