String to an integer in Java MCQ

 converting a string to an integer in Java:

Question 1

Which method is commonly used to convert a String to an int in Java?

A) Integer.toString()

B) String.parseInt()

C) Integer.parseInt()

D) Integer.valueOfString()

Answer: C) Integer.parseInt()

Question 2

What will be the output of the following code?

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String str = "123";

int number = Integer.parseInt(str);

System.out.println(number);

A) 123

B) "123"

C) Error

D) 0

Answer: A) 123

Question 3

What exception is thrown if the string passed to Integer.parseInt() cannot be converted to an integer?

A) NullPointerException

B) NumberFormatException

C) IllegalArgumentException

D) ArithmeticException

Answer: B) NumberFormatException

Question 4

Which of the following code snippets correctly converts a string "456" to an integer?

A) int num = Integer.valueOf("456");

B) int num = Integer.parseInt("456");

C) int num = new Integer("456");

D) All of the above

Answer: D) All of the above

Question 5

What is the difference between Integer.parseInt() and Integer.valueOf() when converting a string to an integer?

A) Integer.parseInt() returns an Integer object, while Integer.valueOf() returns an int.

B) Integer.parseInt() returns an int, while Integer.valueOf() returns an Integer object.

C) Integer.parseInt() throws a NumberFormatException for null strings, while Integer.valueOf() does not.

D) There is no difference.

Answer: B) Integer.parseInt() returns an int, while Integer.valueOf() returns an Integer object.

Question 6

Which of the following is a valid syntax to parse a string "789" into an int using Integer.parseInt()?

A) Integer.parseInt(789);

B) Integer.parseInt("789");

C) Integer.parseInt(new String("789"));

D) B and C

Answer: D) B and C

Question 7

What will happen if the string "12.34" is passed to Integer.parseInt()?

A) It will return 12.

B) It will throw a NumberFormatException.

C) It will return 0.

D) It will return 1234.

Answer: B) It will throw a NumberFormatException.

Question 8

What will be the output of the following code?

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String str = null;

int number = Integer.parseInt(str);

System.out.println(number);

A) 0

B) null

C) It will throw a NullPointerException.

D) It will throw a NumberFormatException.

Answer: D) It will throw a NumberFormatException.

Question 9

Is it possible to convert a string containing only whitespace characters to an int using Integer.parseInt()?

A) Yes

B) No

C) Only if whitespace is trimmed first

D) Only for leading whitespace

Answer: B) No

Question 10

Which class in Java provides the parseInt method?

A) String

B) Integer

C) Double

D) Math

Answer: B) Integer

Question 11

What will the following code return?

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Integer.valueOf("010");

A) 10

B) 8

C) 2

D) It will throw a NumberFormatException.

Answer: A) 10

Question 12

Can Integer.parseInt() be used with a radix other than 10?

A) No, it always uses decimal.

B) Yes, by passing the radix as a second argument.

C) Yes, by changing the default radix.

D) No, it's only for hexadecimal.

Answer: B) Yes, by passing the radix as a second argument.

Question 13

What will the following code output?

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String str = "0";

int number = Integer.parseInt(str);

System.out.println(number);

A) 0

B) "0"

C) Null

D) It will throw a NumberFormatException.

Answer: A) 0

Question 14

Which method would you use to convert a string "1024" into an Integer object?

A) Integer.getInteger("1024");

B) Integer.toString("1024");

C) Integer.valueOf("1024");

D) Integer.parseInt("1024");

Answer: C) Integer.valueOf("1024");

Question 15

What will be the result of Integer.parseInt("1000", 2);?

A) 1000

B) 8

C) 16

D) It will throw a NumberFormatException.

Answer: D) It will throw a NumberFormatException.

Question 16

What will be the result of Integer.parseInt("FF", 16);?

A) 255

B) 256

C) 127

D) It will throw a NumberFormatException.

Answer: A) 255

Question 17

What will be the output of the following code?

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String str = "2147483648";

int number = Integer.parseInt(str);

System.out.println(number);

A) 2147483648

B) -2147483648

C) It will throw a NumberFormatException.

D) 0

Answer: C) It will throw a NumberFormatException.

Question 18

How can you convert a hexadecimal string "1A" to an integer?

A) Integer.parseInt("1A");

B) Integer.parseInt("1A", 16);

C) Integer.parseInt("1A", 10);

D) Integer.valueOf("1A", 10);

Answer: B) Integer.parseInt("1A", 16);

Question 19

Which of the following will convert the string "007" to the integer 7?

A) Integer.valueOf("007");

B) Integer.parseInt("007");

C) new Integer("007");

D) All of the above

Answer: D) All of the above

Question 20

If Integer.parseInt("abc123") is executed, what will be the result?

A) It will return 123.

B) It will return 0.

C) It will return -1.

D) It will throw a NumberFormatException.

Answer: D) It will throw a NumberFormatException.