Wrapper classes in Java MCQ

 Here are multiple-choice questions (MCQs) on wrapper classes in Java:

Question 1

What is the purpose of wrapper classes in Java?

A) To wrap primitive data types into objects.

B) To handle I/O operations.

C) To manage exceptions.

D) To perform arithmetic operations.

Answer: A) To wrap primitive data types into objects.

Question 2

Which wrapper class corresponds to the primitive type int?

A) Double

B) Character

C) Integer

D) Float

Answer: C) Integer

Question 3

Which of the following is NOT a wrapper class in Java?

A) Integer

B) Double

C) Boolean

D) List

Answer: D) List

Question 4

How do you convert a primitive int to an Integer object?

A) Integer i = new Integer(10);

B) Integer i = 10;

C) Integer i = int(10);

D) Integer i = Integer.parseInt(10);

Answer: A) Integer i = new Integer(10);

Question 5

Which method of the Integer class converts a string to an integer?

A) Integer.toString()

B) Integer.parseInt()

C) Integer.valueOf()

D) Integer.convert()

Answer: B) Integer.parseInt()

Question 6

Which of the following statements is true about the Double wrapper class?

A) Double is used to wrap primitive float values.

B) Double provides methods to convert between double and String.

C) Double can only be used with double literals.

D) Double has a method called doubleValue() that returns a float.

Answer: B) Double provides methods to convert between double and String.

Question 7

Which method returns the primitive boolean value from a Boolean object?

A) booleanValue()

B) getBoolean()

C) toBoolean()

D) parseBoolean()

Answer: A) booleanValue()

Question 8

What is the default value of a wrapper class object when it is declared as a field in a class?

A) null

B) 0

C) false

D) NaN

Answer: A) null

Question 9

How do you create a Character object from a primitive char value?

A) Character c = new Character('a');

B) Character c = 'a';

C) Character c = Character.valueOf('a');

D) Character c = Character.parseChar('a');

Answer: A) Character c = new Character('a');

Question 10

Which wrapper class provides a constant for the maximum value of its type?

A) Integer

B) Boolean

C) Double

D) Character

Answer: A) Integer

Question 11

Which of the following is NOT a method provided by the Float wrapper class?

A) floatValue()

B) toString()

C) parseFloat()

D) getFloat()

Answer: D) getFloat()

Question 12

What is the result of calling Integer.parseInt("123")?

A) 123.0

B) 123

C) null

D) Integer("123")

Answer: B) 123

Question 13

How can you convert a Boolean object to a primitive boolean value?

A) Boolean.toPrimitive()

B) Boolean.getValue()

C) Boolean.booleanValue()

D) Boolean.parseBoolean()

Answer: C) Boolean.booleanValue()

Question 14

Which method of the Character class checks if a character is a digit?

A) Character.isDigit()

B) Character.isNumber()

C) Character.isDigitOrLetter()

D) Character.isNumeric()

Answer: A) Character.isDigit()

Question 15

Which wrapper class is used to represent a float data type?

A) Float

B) Double

C) Long

D) Integer

Answer: A) Float

Question 16

Which method of the Integer class returns the integer value represented by the specified string argument?

A) Integer.parseInt()

B) Integer.toInt()

C) Integer.valueOf()

D) Integer.getValue()

Answer: A) Integer.parseInt()

Question 17

Which of the following methods is used to compare two Double objects?

A) Double.compare()

B) Double.equals()

C) Double.compareTo()

D) Double.isEqual()

Answer: A) Double.compare()

Question 18

How do you obtain the primitive long value from a Long object?

A) longValue()

B) getLong()

C) toLong()

D) Long.valueOf()

Answer: A) longValue()

Question 19

What is the maximum value that can be held by an Integer wrapper class?

A) 2147483647

B) Infinity

C) 127

D) Double.MAX_VALUE

Answer: A) 2147483647

Question 20

Which wrapper class provides the method toString() to convert its value to a String?

A) Integer

B) Boolean

C) Double

D) All of the above

Answer: D) All of the above