Java Interview Question Answers (2023)

In this blog post, we will discuss Java interview questions with answers, (Java Interview Questions Answers (2023), here we have provided you with top 50 questions and answers related to Java programming language, which are asked in interview, that is important for freshers. If you go for an interview in any IT sector company, then all these questions are definitely asked. That’s why we have prepared top 50 questions and answers for you on this blog related Java Programming Language.

Java Short Introduction

Java is a high-level, object-oriented programming language that is widely used for developing desktop, web, and mobile applications. It was developed by James Gosling at Sun Microsystems (now owned by Oracle Corporation) in the mid-1990s. Java is known for its platform independence, meaning that it can run on any operating system with a Java Virtual Machine (JVM) installed. Java is also popular for its robustness, reliability, and security features. It is used by millions of developers and companies worldwide.

Java Interview Question with Answers (2023)

Question 1. What is Java?

Answer: Java is a popular object-oriented programming language that is used to create a variety of applications, from web applications to mobile applications.

 

Questions 2. What is the difference between an abstract class and an interface in Java?

Answer: An abstract class can have non-abstract methods and member variables, while an interface in Java contains only abstract methods.

 

Question 3. What is a JVM?

Answer: A JVM (Java Virtual Machine) is a software that allows Java code to run on different platforms and devices.

 

Question 4. What is a package in Java?

Answer: A package is a namespace that organizes a set of related classes and interfaces in Java.

 

Question 5. What is inheritance in Java?

Answer: Inheritance is a mechanism in Java that allows a class to inherit properties and behavior from another class.

 

Question 6. What is polymorphism in Java?

Answer: Polymorphism is a feature in Java that allows objects of different classes to be treated as if they were of the same class.

 

Question 7. What is encapsulation in Java?

Answer: Encapsulation is a feature in Java that allows the internal state of an object to be hidden from the outside world.

 

Question 8. What is the difference between a class and an object in Java?

Answer: A class is a blueprint for creating objects, while an object is an instance of a class.

 

Question 9. What is a constructor in Java?

Answer: A constructor is a special method in Java that is used to initialize objects.

 

Question 10. What is a static method in Java?

Answer: A static method in Java is a method that belongs to the class rather than to an instance of the class.

 

Question 11. What is a final variable in Java?

Answer: A final variable in Java is a variable whose value cannot be changed once it has been initialized.

 

Question 12. What is an abstract method in Java?

Answer: An abstract method in Java is a method that is declared but does not have an implementation.

 

Question 13. What is a synchronized method in Java?

Answer: A synchronized method in Java is a method that can only be accessed by one thread at a time.

 

Question 14. What is the difference between an ArrayList and a LinkedList in Java?

Answer: An ArrayList in Java is implemented as an array, while a LinkedList is implemented as a linked list.

 

Question 15. What is the difference between a HashSet and a TreeSet in Java?

Answer: A HashSet in Java is an unordered collection of objects, while a TreeSet is an ordered collection of objects.

Java Interview Question Answers (2023)

Question 16. What is the difference between a stack and a queue in Java?

Answer: A stack in Java is a Last-In-First-Out (LIFO) collection of objects, while a queue is a First-In-First-Out (FIFO) collection of objects.

 

Question 17. What is the difference between a HashMap and a TreeMap in Java?

Answer: A HashMap in Java is an unordered collection of key-value pairs, while a TreeMap is an ordered collection of key-value pairs.

 

Question 18. What is the difference between an interface and an abstract class in Java?

Answer: An interface in Java contains only abstract methods, while an abstract class can contain both abstract and non-abstract methods.

 

Question 19. What is the difference between a public, private, and protected modifier in Java?

Answer: A public modifier in Java allows a class, method, or variable to be accessed from anywhere, while a private modifier restricts access to only the same class, and a protected modifier allows access to the same class and any subclass.

 

Question 20. What is the difference between a checked and an unchecked exception in Java?

Answer: A checked exception in Java must be handled by the calling method or thrown, while an unchecked exception does not have to be handled or declared.

 

Question 21. What is the difference between a compiler and an interpreter in Java?

Answer: A compiler in Java converts source code into bytecode, while an interpreter executes bytecode directly.

 

Question 22. What is the difference between a classpath and a module path in Java?

Answer: A classpath in Java is a set of directories and JAR files that are searched for classes and resources, while a module path is used to specify dependencies between modules.

 

Question 23. What is a lambda expression in Java?

Answer: A lambda expression in Java is a way to define a method without creating a class.

 

Question 24. What is a stream in Java?

Answer: A stream in Java is a sequence of data elements that can be processed in a functional style.

 

Question 25. What is a functional interface in Java?

Answer: A functional interface in Java is an interface that contains only one abstract method and can be used as the basis for a lambda expression.




Question 26. What is the difference between a stream and a collection in Java?

Answer: A stream in Java is a sequence of data elements that can be processed in a functional style, while a collection is a container of elements.

 

Question 27. What is the difference between a StringBuilder and a StringBuffer in Java?

Answer: A StringBuilder in Java is not synchronized and is therefore faster, while a StringBuffer is synchronized and is therefore safer in multithreaded environments.

 

Question 28. What is a try-with-resources stat ement in Java?

Answer: A try-with-resources statement in Java is a way to automatically close resources such as files, sockets, and database connections.

 

Question 29. What is the diamond operator in Java?

Answer: The diamond operator in Java is a shorthand way to create generic objects without specifying the type parameters.

 

Question 30. What is the difference between a local variable and an instance variable in Java?

Answer: A local variable in Java is a variable that is declared inside a method or block and has a limited scope, while an instance variable is a variable that is declared inside a class and can be accessed by any method or block in that class.

 

Question 31. What is the difference between a primitive data type and an object in Java?

Answer: A primitive data type in Java is a basic data type such as int, boolean, or double, while an object is an instance of a class.

Question 32. What is the difference between == and equals() in Java?

Answer: == in Java compares object references, while equals() compares the contents of objects.

 

Question 33. What is the difference between a for loop and a for-each loop in Java?

Answer: A for loop in Java is used to iterate over a sequence of elements, while a for-each loop is used to iterate over the elements of a collection.

 

Question 34. What is a marker interface in Java?

Answer: A marker interface in Java is an interface that contains no methods and is used to provide metadata to the Java runtime environment.

 

Question 35. What is a Java Bean in Java?

Answer: A Java Bean in Java is a reusable software component that conforms to a set of naming and design conventions.

Java Interview Question Answers (2023)

Question 36. What is the difference between an error and an exception in Java?

Answer: An error in Java indicates a serious problem that cannot be handled by the application, while an exception indicates a problem that can be handled by the application.

 

Question 37. What is the difference between a “public static void main()” method and a regular method in Java?

Answer: The “public static void main()” method in Java is the entry point for a Java application, while a regular method is a method that is called from other parts of the code.

 

Question 38. What is the difference between a shallow copy and a deep copy in Java?

Answer: In Java, a shallow copy creates a new object that references the same memory locations as the original object, while a deep copy creates a new object with its own memory locations and copies all the values of the original object. A shallow copy is faster and simpler, but changes to the copy will affect the original object, while a deep copy creates a new, independent object.

 

Question 39. What is the difference between a runtime exception and a checked exception in Java?

Answer: A runtime exception in Java indicates a problem that could not be detected at compile-time, while a checked exception is a type of exception that must be declared in the method signature or handled in a try-catch block.

 

Question 40. What is the difference between a superclass and a subclass in Java?

Answer: A superclass in Java is a class that is extended by another class, while a subclass is a class that extends another class.

 

Question 41. What is polymorphism in Java?

Answer: Polymorphism in Java is the ability of objects to take on different forms depending on the context in which they are used.

 

Question 42. What is the difference between a private and a protected access modifier in Java?

Answer: A private access modifier in Java restricts access to a variable or method to the class in which it is declared, while a protected access modifier allows access to the variable or method from within the class and any subclasses.

 

Question 43. What is the purpose of the final keyword in Java?

Answer: The final keyword in Java is used to indicate that a variable, method, or class cannot be modified.

 

Question 44. What is the purpose of the static keyword in Java?

Answer: The static keyword in Java is used to indicate that a variable or method belongs to the class rather than to an instance of the class.

 

Question 45. What is the purpose of the synchronized keyword in Java?

Answer: The synchronized keyword in Java is used to ensure that only one thread can access a block of code or a method at a time.

 

Question 46. What is the purpose of the transient keyword in Java?

Answer: The transient keyword in Java is used to indicate that a variable should not be serialized when the object is written to a stream.

 

Question 47. What is the purpose of the volatile keyword in Java?

Answer: The volatile keyword in Java is used to indicate that a variable may be modified by multiple threads and that the value should be read directly from memory.

 

Question 48. What is the purpose of the assert statement in Java?

Answer: The assert statement in Java is used to check that a condition is true and to throw an AssertionError if it is not.

 

Question 49. What is the difference between the break and continue statements in Java?

Answer: The break statement in Java is used to terminate a loop or switch statement, while the continue statement is used to skip the current iteration of a loop.

 

Question 50. What is the purpose of the “this keyword” in Java?

Answer: The “this keyword” in Java is used to refer to the current object instance.

Conclusion

So, you learned here Top 50 Java Interview Question Answers (2023), all these questions are very important, if you are from IT sector. I hope you have understood all questions and answers very well and if you have any doubt, regarding it then you can ask in the comment section.

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