Java Autoboxing MCQs Questions

21

What is the result of the following code in Java?
Integer num = null;
int result = num + 5;

A) `5` B) `null` C) `Compilation error` D) `Runtime error`

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Answer & Solution

Answer: Option C

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22

In Java, which of the following is an example of autounboxing?

A) `String text = "Hello";` B) `int value = Integer.parseInt("42");` C) `Double result = 3.14;` D) None of These

Discuss

Answer & Solution

Answer: Option D

Solution:

Autounboxing in Java refers to the automatic conversion of a wrapper class object to its corresponding primitive type.

For example, converting an Integer object to an int, or a Double object to a double.

Let's examine the options:

Option A: String text = "Hello"; — This is just assigning a String literal to a String variable, not related to autounboxing.

Option B: int value = Integer.parseInt("42"); — This parses a String to a primitive int, but it does not involve autounboxing because no wrapper object is involved.

Option C: Double result = 3.14; — This is an example of autoboxing (primitive to wrapper), not autounboxing.

Since none of the options demonstrate converting a wrapper object to a primitive type, the correct answer is None of These.

23

What happens if you try to unbox a `null` reference in Java?

A) It throws a `ClassCastException` B) It returns `null` C) It throws a `NullPointerException` D) It returns the default value for the primitive type

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Answer & Solution

Answer: Option C

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24

In Java, what is the result of the expression `new Integer(5) == 5`?

A) `false` B) Compilation error C) Runtime error D) `true`

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Answer & Solution

Answer: Option D

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25

Which of the following is an example of autoboxing in Java?

A) `Character ch = 'A';` B) `String text = "Hello";` C) `int value = 42;` D) `Double result = 3.14;`

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Answer & Solution

Answer: Option A

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26

In Java, which method can be used to perform autounboxing?

A) `.compareTo()` B) `.equals()` C) `.valueOf()` D) `.intValue()`

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Answer & Solution

Answer: Option D

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27

What is the result of the following code in Java?
Integer x = 1000;
Integer y = 1000;
System.out.println(x.equals(y));

A) `false` B) Compilation error C) `true` D) Runtime error

Discuss

Answer & Solution

Answer: Option C

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28

In Java, what is the result of the expression `new Integer(5).equals(5)`?

A) Compilation error B) `true` C) Runtime error D) None of These

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Answer & Solution

Answer: Option B

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29

What is the result of the following code in Java?
Integer num1 = 100;
Integer num2 = 100;
System.out.println(num1 == num2);

A) Runtime error B) Compilation error C) `true` D) `false`

Discuss

Answer & Solution

Answer: Option C

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30

In Java, what is the result of the expression `Integer.valueOf(10).equals(Integer.valueOf(10))`?

A) `false` B) Compilation error C) Runtime error D) `true`

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Answer & Solution

Answer: Option D

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Java Autoboxing MCQs Questions | Java Program MCQs