Java Regex Quiz - MCQ - Multiple Choice Questions

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 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 

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

a) Pattern 

b) Matcher 

c) RegularExpression 

d) Regex 

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 

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

a) compile() 

b) parse() 

c) pattern() 

d) regex() 

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

a) * 

b) + 

c) ? 

d) {} 

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

a) \

b) ^ 

c) $ 

d) # 

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 

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() 

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() 

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] 

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

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

Answers and Explanations

Question 1

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.

Question 2

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.

Question 3

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.

Question 4

Answer:

a) compile()

Explanation:

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

Question 5

Answer:

c) ? 

Explanation:

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

Question 6

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.

Question 7

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.

Question 8

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.

Question 9

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.

Question 10

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.

Question 11

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".

Question 12

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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Check out 100+ quiz questions: 100+ Quiz Questions to Test Your Java, Spring Boot, Microservices, Hibernate, REST API Skills

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