Object-Oriented Programming Concepts

Object-oriented programming (OOP) is a fundamental programming paradigm in Java. Key concepts include classes, objects, inheritance, polymorphism, encapsulation, and abstraction. Mastering these concepts is essential for any Java developer.

To explore OOP concepts in detail, visit our article: Object-Oriented Programming Concepts.

Questions and Answers

1. What is a class?

A class is a blueprint for creating objects in OOP.

2. What is an object?

An object is an instance of a class.

3. What is inheritance?

Inheritance is a mechanism where a new class inherits properties and behavior from an existing class.

4. What is polymorphism?

Polymorphism allows methods to do different things based on the object it is acting upon.

5. What is encapsulation?

Encapsulation is the bundling of data and methods that operate on that data within one unit, typically a class.

6. What is abstraction?

Abstraction is the concept of hiding the complex reality while exposing only the necessary parts.

7. What is a constructor?

A constructor is a special method used to initialize objects.

8. What is method overloading?

Method overloading allows multiple methods to have the same name with different parameters.

9. What is method overriding?

Method overriding allows a subclass to provide a specific implementation of a method that is already defined in its superclass.

10. What is an interface?

An interface is a reference type in Java, similar to a class, that can contain only constants, method signatures, default methods, static methods, and nested types.

11. What is an abstract class?

An abstract class cannot be instantiated and can contain abstract methods that must be implemented by subclasses.

12. What is the difference between an interface and an abstract class?

An interface can only contain method signatures and final variables, while an abstract class can have method implementations and instance variables.

13. What is a package?

A package is a namespace that organizes a set of related classes and interfaces.

14. What is the purpose of the 'this' keyword?

The 'this' keyword refers to the current object in a method or constructor.

15. What is the purpose of the 'super' keyword?

The 'super' keyword is used to refer to the immediate parent class object.

16. What is a static method?

A static method belongs to the class rather than any specific instance and can be called without creating an object.

17. What is a final class?

A final class cannot be subclassed.

18. What is a final method?

A final method cannot be overridden by subclasses.

19. What is a final variable?

A final variable cannot be reassigned once it has been initialized.

20. What is a constructor overloading?

Constructor overloading allows a class to have more than one constructor with different parameters.

21. What is a nested class?

A nested class is a class defined within another class.

22. What is a local class?

A local class is defined within a method and can only be accessed within that method.

23. What is an anonymous class?

An anonymous class is a class without a name that is declared and instantiated in a single statement.

24. What is the difference between == and .equals()?

== checks for reference equality, while .equals() checks for value equality.

25. What is a Java Bean?

A Java Bean is a reusable software component that follows certain conventions, including having a no-argument constructor and providing getter and setter methods.

26. What is the Java Collections Framework?

The Java Collections Framework is a set of classes and interfaces that implement commonly reusable collection data structures.

27. What is a List?

A List is an ordered collection that can contain duplicate elements.

28. What is a Set?

A Set is a collection that cannot contain duplicate elements.

29. What is a Map?

A Map is an object that maps keys to values, where each key is unique.

30. What is the difference between ArrayList and LinkedList?

ArrayList is backed by an array and provides fast random access, while LinkedList is backed by a doubly linked list and provides faster insertions and deletions.

31. What is a HashMap?

A HashMap is a Map that uses a hash table for storage, allowing for fast retrieval based on keys.

32. What is a TreeMap?

A TreeMap is a Map that is sorted according to the natural ordering of its keys or by a comparator provided at map creation time.

33. What is a Stack?

A Stack is a collection that follows the Last In First Out (LIFO) principle.

34. What is a Queue?

A Queue is a collection that follows the First In First Out (FIFO) principle.

35. What is a thread?

A thread is a lightweight process that can run concurrently with other threads.

36. What is synchronization?

Synchronization is the process of controlling access to shared resources by multiple threads.

37. What is a deadlock?

A deadlock is a situation where two or more threads are blocked forever, waiting for each other.

38. What is exception handling?

Exception handling is a mechanism to handle runtime errors, allowing the program to continue its execution.

39. What is a try-catch block?

A try-catch block is used to catch exceptions that may occur in the try block and handle them in the catch block.

40. What is a finally block?

A finally block is used to execute code after a try-catch block, regardless of whether an exception was thrown or not.

41. What is a checked exception?

A checked exception is an exception that must be either caught or declared in the method signature.

42. What is an unchecked exception?

An unchecked exception is an exception that does not need to be declared or caught.

43. What is a lambda expression?

A lambda expression is a concise way to represent an anonymous function that can be passed around as a parameter.

44. What is a stream in Java?

A stream is a sequence of elements that can be processed in a functional style.

45. What is the difference between a stream and a collection?

A collection is a data structure that stores elements, while a stream is a sequence of elements that can be processed.

46. What is the Java Virtual Machine (JVM)?

The JVM is an abstract computing machine that enables a computer to run Java programs.

47. What is the Java Runtime Environment (JRE)?

The JRE is a package that provides the libraries, Java Virtual Machine (JVM), and other components to run Java applications.

48. What is the Java Development Kit (JDK)?

The JDK is a software development kit that provides tools for developing Java applications, including the JRE.

49. What is garbage collection?

Garbage collection is the process of automatically freeing memory by deleting objects that are no longer in use.

50. What is the difference between String, StringBuilder, and StringBuffer?

String is immutable, while StringBuilder and StringBuffer are mutable. StringBuffer is synchronized, making it thread-safe, while StringBuilder is not.

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