Java MCQs – Classes and Objects

21.) What is a class in Java?

A) An instance of an object
B) A template for creating objects
C) A predefined method in Java
D) A data type for variables

Answer: Option B

Explanation: A class in Java defines a blueprint for creating objects. It encapsulates attributes (data) and methods (behavior) that define the characteristics and actions of objects.

22.) Which keyword is used to create an instance of a class in Java?

A) new
B) this
C) class
D) object

Answer: Option A

Explanation: The “new” keyword is used to allocate memory and create an instance of a class.

23.) What is an object reference in Java?

A) The memory address of an object
B) The name of a class
C) A keyword for creating objects
D) A variable that holds the memory location of an object

Answer: Option D

Explanation: An object reference is a variable that stores the memory address of an object, allowing you to access and manipulate the object.

24.) Which of the following is a valid way to access an instance variable of an object in Java?

A) ClassName.variableName
B) objectName.variableName
C) variableName.objectName
D) variableName.ClassName

Answer: Option B

Explanation: Instance variables are accessed using the object name followed by the dot operator.

25.) What is the “constructor” of a class in Java?

A) A method used for destroying objects
B) A reserved keyword indicating class creation
C) A method used to initialize objects
D) A method used for inheritance

Answer: Option C

Explanation: A constructor is a special method in a class used to initialize the attributes of an object when it is created.

26.) Which of the following is true about the default constructor in Java?

A) It takes parameters and initializes object attributes.
B) It is provided by the compiler if no constructor is defined.
C) It is used to destroy objects.
D) It can be overloaded with multiple constructors.

Answer: Option B

Explanation: If no constructor is explicitly defined in a class, the compiler provides a default constructor that initializes attributes to default values.

27.) What is the relationship between a method and an object in Java?

A) A method is an object.
B) An object is a method.
C) A method operates on an object’s data and behavior.
D) A method creates objects.

Answer: Option C

Explanation: Methods define the actions that an object can perform and operate on the object’s attributes (data) and methods (behavior).

28.) In Java, can a class have multiple methods with the same name but different parameters?

A) Yes, but it is discouraged.
B) No, it will result in a compilation error.
C) Yes, and it is called method overloading.
D) No, it violates encapsulation principles.

Answer: Option C

Explanation: Method overloading allows a class to have multiple methods with the same name but different parameter lists, providing flexibility and clarity.

29.) What is the purpose of the “static” keyword in Java class members (fields and methods)?

A) It indicates that the member is dynamically allocated.
B) It signifies that the member belongs to the object.
C) It indicates that the member is shared among all instances of the class.
D) It is used to override methods.

Answer: Option C

Explanation: The “static” keyword is used to define class-level variables (static fields) and methods (static methods) that are shared among all instances of the class.

30.) What is the access modifier used to specify that a class member can be accessed by any class in the same package?

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

Answer: Option D

Explanation: The default access modifier (no modifier) allows class members to be accessible within the same package but not outside it.

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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