Java Regex Basics and Pattern Matching

Here are 10 essential multiple-choice questions on Java Regex Basics and Pattern Matching, covering key concepts.

Last Updated : Apr 25, 2025

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Question 1

What does the Pattern class in Java represent?

A
It is a class that provides methods to match regular expressions
B
It is a class that stores strings for future matching
C
It is a class used to compile a regular expression into a pattern object
D
It is a class used to represent strings without any pattern matching

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Question 2

Which of the following is a method of the Matcher class used to check if a string matches the pattern?

A
find()
B
search()
C
matches()
D
isMatch()

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Question 3

Consider the following code snippet. What will be the output of this code?

Java

import java.util.regex.*;

public class Main {
    public static void main(String[] args) {
        String regex = "a*b";
        String input = "aaab";
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(input);
        System.out.println(matcher.matches());
    }
}

A
true
B
false
C
aaab
D
Compile-time error

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Question 4

What does the find() method of the Matcher class do?

A
It checks if the entire string matches the pattern
B
It finds the next occurrence of the pattern in the input string
C
It replaces the matched string with another string
D
It splits the string based on the regular expression

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Question 5

Which of the following regular expression patterns represents a digit in Java?

A
\\D
B
\\w
C
\\W
D
\\d

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Question 6

What is the purpose of the Character class in the context of Java regex?

A
It is used to represent a character within a pattern
B
It is used to define the case sensitivity of regular expressions
C
It helps in escaping characters in a regular expression
D
It is used to create a regular expression pattern dynamically

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Question 7

How do you escape special characters in a Java regular expression?

A
By using the backslash (\)
B
By using double backslash (\\)
C
By using a Matcher object
D
By using parentheses ()

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Question 8

Which of the following will match a string that starts with a digit followed by any number of lowercase letters?

A
^\\d[A-Z]*$
B
^\\d[a-z]+$
C
^\\d[a-z]*$
D
\\d[a-z]*$

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Question 9

What is the purpose of the Pattern.compile() method in Java regex?

A
It matches a string with the provided pattern
B
It creates a new Matcher object from a regular expression pattern
C
It converts a regular expression into a human-readable format
D
It compiles a string into a regular expression pattern object

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Question 10

Consider the following regular expression pattern \\w+. What will it match?

A
One or more word characters (letters, digits, and underscores)
B
One or more non-word characters
C
Any character except a word character
D
Zero or more word characters

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