Java MCQs – Classes and Objects

11.) What is the main difference between a class and an object in Java?

A) A class is a blueprint, while an object is an instance of a class.
B) A class is an instance of an object, while an object is a blueprint.
C) A class and an object are the same thing.
D) A class defines attributes, while an object defines methods.

Answer: Option A

Explanation: A class defines the structure (attributes and methods) for creating objects, while an object is a specific instance created from that class.

12.) Which of the following best describes the concept of data abstraction in Java?

A) Hiding the internal implementation details of an object
B) Accessing object attributes using the “this” keyword
C) Creating a new class based on an existing class
D) Using “get” and “set” methods for data manipulation

Answer: Option A

Explanation: Data abstraction involves presenting only essential information and hiding the unnecessary details of an object’s implementation.

13.) Which section of a class contains the class’s attributes and instance variables?

A) Method section
B) Object section
C) Instance section
D) Field section

Answer: Option D

Explanation: The field section of a class contains the class’s attributes and instance variables.

14.) What is the purpose of the “toString” method in Java?

A) To convert a class to a string representation
B) To convert an object to an integer
C) To compare two objects for equality
D) To create a new object from an existing one

Answer: Option A

Explanation: The “toString” method is used to provide a string representation of an object for display or printing.

15.) What is a default constructor in Java?

A) A constructor with no parameters that are provided by the compiler
B) A constructor that is automatically generated for static methods
C) A constructor that creates a new instance of a class
D) A constructor with the “default” access modifier

Answer: Option A

Explanation: A default constructor is automatically generated by the compiler if no constructor is explicitly defined in a class.

16.) Which keyword is used to access the superclass’s members (fields and methods) from a subclass?

A) super
B) this
C) parent
D) base

Answer: Option A

Explanation: The “super” keyword is used to access the superclass’s members and methods from a subclass.

17.) In Java, can an object of a subclass be assigned to a variable of the superclass type?

A) No, it will result in a compilation error.
B) Yes, but only if the subclass overrides superclass methods.
C) Yes, this is allowed and is called polymorphism.
D) Yes, but only if the subclass has the same name as the superclass.

Answer: Option C

Explanation: Polymorphism allows an object of a subclass to be treated as an object of the superclass type, enabling flexibility and code reuse.

18.) Which access modifier makes a class member accessible only within the same class?

A) private
B) protected
C) public
D) default (package-private)

Answer: Option A

Explanation: The “private” access modifier restricts access to the member to within the same class only.

19.) What is the purpose of a “getter” method in Java?

A) To modify the value of an attribute
B) To provide access to the value of an attribute
C) To create a new instance of a class
D) To override superclass methods

Answer: Option B

Explanation: A “getter” method is used to retrieve the value of an attribute (instance variable) from an object.

20.) What is the role of the “equals” method in Java?

A) To compare the memory addresses of two objects
B) To compare the attributes of two objects for equality
C) To create a new instance of a class
D) To override superclass methods

Answer: Option B

Explanation: The “equals” method is used to compare the attributes (contents) of two objects to determine if they are equal.

Java logical programs list

Java Basic Programs

  1. Java Hello world program
  2. Java Program to Add two Numbers
  3. Java Program to Subtract two Numbers
  4. Java Program to Multiply two Numbers
  5. Java Program to Check Whether a Number is Even or Odd.
  6. Check whether a character is a Vowel or Consonant.
  7. Java Program to find Average of Two Numbers
  8. Java Program to find Average of Three Numbers
  9. Java Program to find the Area of Square
  10. Java Program to Calculate Simple Interest
  11. Java Program to Calculate Compound Interest
  12. List of basic logical programs in Java
  13. How to print a Fibonacci series up to a given number in Java?
  14. How to calculate the factorial of a given number in java?
  15. How to check whether an integer number is a prime number or not in java?
  16. How to check whether a number is a perfect number or not in java?
  17. How to check whether a number is an Armstrong number or not in java?
  18. How to reverse a number in Java?
  19. How to check whether a number is a Palindrome number or not in Java?
  20. How to swap two numbers without using a third variable in Java?
  21. How to reverse a string without using the reverse() method in java?
  22. How to check whether a String is a Palindrome or not in java?
  23. How to count characters from the string in java?
  24. How to check if two strings are anagrams of each other?
  25. How to count the occurrence of the given character in a string in java?
  26. How to swap two strings without using the third variable in java?

Java Pattern Printing Programs

  1. Star pattern programs [Tricks] in Java
  2. Top 30-star pattern programs in java
  3. Top 10 Number pattern programs in java
  4. Top 10 Character pattern programs in java
  5. Top 50 Pattern printing programs in java
  6. Pyramid Pattern.
  7. Diamond Pattern.
  8. Hollow Diamond Pattern.

Java Series Printing Programs

  1. Print a Fibonacci series
  2. Even Numbers Series
  3. Odd Numbers Series
  4. Square Numbers Series
  5. Cube Numbers Series
  6. Print Series 1,2,9,28,65
  7. Java Program to Print Series 1,2,5,10,17
  8. Java Program to Print Series 2,4,8,16,32

Java Array-Based Programs

  1. Copy an Array
  2. Merge Two Arrays.
  3. Sum of Two Arrays.
  4. Print Odd/Even No. from an Array.
  5. Find the Sum of an Array
  6. Sum of Even Numbers in an Array.
  7. Average of Odd/Even Numbers in Array.
  8. Calculate Average Using Array
  9. Find the Smallest Number in an Array.
  10. Find the Largest Number in an Array.
  11. 2nd Largest Number in an Array.
  12. Remove duplicate elements in an Array.

Multi-Dimensional Array Programs

  1. Print Matrix or 2D Array.
  2. Read a Matrix from the User.
  3. Add the Two Matrices.
  4. Subtract the Two Matrices.
  5. Matrix Multiplication.
  6. Identity Matrix Program.
  7. Symmetric Matrix Program.
  8. Find the Transpose of a Matrix.
  9. Find the Smallest Element in a Matrix.
  10. Find the Largest Element in a Matrix.
  11. Search Matrix.
  12. The sum of Diagonals of a Matrix.

Java String Programs

  1. String length without using length() method.
  2. Count the Number of Vowels in a String.
  3. Swap two strings without using the third variable.
  4. Reverse a string without using the reverse() method.
  5. Reverse the words in a given string sentence
  6. Check whether a String is a Palindrome or not in Java.
  7. Count characters from the string in Java.
  8. Count the number of words in the String.
  9. Check if the two strings are anagrams of each other.
  10. Count the occurrence of the given character in a string.
  11. Find the Maximum Occurring Character in a String
  12. Find the First non-repeating Character in a given String
  13. Remove all Duplicates from a given String
  14. Remove a given character from the String
  15. Find the Sum of Digits in a String.
  16. Compare two Strings in Java.
  17. String Permutations Program in Java
  18. Combinations of String in Java

Java Conversion Programs

  1. Binary to Decimal
  2. Binary to Decimal using Recursion
  3. Decimal to Binary
  4. Decimal to Octal
  5. Decimal to Hexadecimal
  6. Fahrenheit to Celsius
  7. Celsius to Fahrenheit

Java Miscellaneous Programs

  1. Generate Random String in Java
  2. Generating Random Numbers in Java
  3. Generating OTP in Java
  4. Secret Message Program in Java

Java Game Programs

  1. Tic-Tac-Toe Game in Java
  2. Hangman Game in Java
  3. Rock Paper Scissors Game in Java
  4. Number Guessing Game in Java
  5. Word Search Solver Game in Java
  6. Tower of Hanoi Game in Java

Java Programs based on the Collection Framework

  1. ArrayList Manipulation: add, remove Elements, find size
  2. Write a Java program to reverse a List without using the built-in Collections.reverse() method.
  3. Find duplicate elements in an ArrayList
  4. Implement a Java program to sort an ArrayList of integer numbers.
  5. Implement a Java program to sort an ArrayList of custom objects based on a specific attribute.
  6. Create a stack using an ArrayList and implement push, pop, and peek operations.
  7. Convert an ArrayList of strings into a string array.
  8. Write a Java program to remove all elements from an ArrayList that are greater than a certain value.
  9. Write a Java program to remove duplicates from an ArrayList while preserving the original order.
  10. Write a Java program to find the common elements in two given ArrayLists.
  11. ArrayList partition into two separate lists of odd/even numbers.
  12. Write a program that extracts a sublist from an ArrayList, given a start and end index.
  13. Merge two sorted ArrayLists into a single sorted ArrayList.
  14. Find unique string in ArrayList with its frequency
  15. Write a program to swap the positions of two elements in an ArrayList given their indices.
  16. Write a program to Create a Custom LinkedList in Java
  17. Write a Java program for Basic Queue Implementation using LinkedList
  18. Write a Java program to create a PriorityQueue to manage a to-do list
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