Java Regex Quiz - MCQ - Multiple Choice Questions

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Welcome to our Java Regular Expressions quiz! Regular expressions are powerful patterns used for matching and manipulating text in Java.

In this blog post, we present a set of multiple-choice questions to test your understanding of Regular expressions in Java. Let's put your knowledge to the test and see how well you grasp this essential aspect of Java programming.

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The answer and explanation of each question have been given at the end of this post.

1. What is a regular expression?

a) A sequence of characters that forms a pattern

b) A special data type in Java

c) A programming language

d) A file format for storing data

Answer:

a) A sequence of characters that forms a pattern

Explanation:

A regular expression is a sequence of characters that forms a pattern used for matching and manipulating text.

2. Which class is used to work with regular expressions in Java?

a) Pattern

b) Matcher

c) RegularExpression

d) Regex

Answer:

a) Pattern

Explanation:

The Pattern class in Java is used to work with regular expressions. It provides methods for compiling and matching patterns against strings.

3. What is the purpose of the Pattern class in Java regular expressions?

a) To define a regular expression pattern

b) To match a pattern against a string

c) To replace matched patterns with a specified string

d) To split a string based on a pattern

Answer:

a) To define a regular expression pattern

Explanation:

The Pattern class is used to define a regular expression pattern. It allows you to specify the pattern using metacharacters, quantifiers, and character classes.

4. What method is used to compile a regular expression pattern into a Pattern object?

a) compile()

b) parse()

c) pattern()

d) regex()

Answer:

a) compile()

Explanation:

The compile() method is used to compile a regular expression pattern into a Pattern object.

5. Which quantifier is used to specify zero or one occurrence of a character in a regular expression?

a) *

b) +

c) ?

d) {}

Answer:

c) ?

Explanation:

The "?" quantifier is used to specify zero or one occurrence of a character in a regular expression.

6. What character is used as an escape character in Java regular expressions?

a) \

b) ^

c) $

d) #

Answer:

a) \

Explanation:

The backslash \ is used as an escape character in Java regular expressions. It allows you to escape metacharacters and treat them as literal characters.

7. What is the purpose of the Matcher class in Java regular expressions?

a) To define a regular expression pattern

b) To compile a regular expression pattern

c) To match a pattern against a string

d) To replace matched patterns with a specified string

Answer:

c) To match a pattern against a string

Explanation:

The Matcher class in Java regular expressions is used to match a pattern against a string. It provides methods for finding, matching, and manipulating text based on the specified pattern.

8. Which method is used to perform a pattern match against a string using a Matcher object?

a) match()

b) find()

c) replaceAll()

d) split()

Answer:

b) find()

Explanation:

The find() method is used to perform a pattern match against a string using a Matcher object. It finds the next occurrence of the pattern in the string.

9. What method is used to find the next occurrence of a pattern in a string using a Matcher object?

a) next()

b) match()

c) find()

d) search()

Answer:

c) find()

Explanation:

The find() method is used to find the next occurrence of a pattern in a string using a Matcher object. It returns true if a match is found; otherwise, it returns false.

10. Which class is used to represent a group of characters in square brackets in a regular expression?

a) CharacterGroup

b) CharacterSet

c) CharGroup

d) [a-zA-Z]

Answer:

b) CharacterSet

Explanation:

The CharacterSet is used to represent a group of characters in a regular expression. It allows you to specify a range of characters or a set of characters to match.

11. What is the output of the following code snippet?

import java.util.regex.*;

public class RegexQuiz {
    public static void main(String[] args) {
        String regex = "\\d+";
        String input = "1234";

        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(input);

        while (matcher.find()) {
            System.out.print(matcher.group() + " ");
        }
    }
}

a) 1

b) 1234

c) 123456789

d) Compile-time error

Answer:

b) 1234

Explanation:

The regex pattern "\\d+" is used, which matches one or more digits. Since the input string "1234" consists of only digits, the regex pattern matches the entire string. Therefore, the output will be "1234".

12. What is the output of the following code snippet?

import java.util.regex.*;

public class RegexQuiz {
    public static void main(String[] args) {
        String regex = "[a-c]";
        String input = "abcABC";

        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(input);

        while (matcher.find()) {
            System.out.print(matcher.group() + " ");
        }
    }
}

a) a b c

b) A B C

c) a b c A B C

d) Compile-time error

Answer:

a) a b c

Explanation:

The regex "[a-c]" matches any character between 'a' and 'c' (inclusive) in a case-sensitive manner. In the input string "abcABC", it matches "a", "b", and "c" and prints them.

Conclusion

Congratulations on completing our Java Regular Expressions quiz! We hope you found it informative and enjoyed testing your knowledge of regular expressions in Java. Regular expressions are a powerful tool for pattern matching and text manipulation.

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Keep exploring and practicing regular expressions to enhance your skills in Java programming.

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