Regex expressions in Java, \\s vs. \\s+

A Regex (Regular Expression) is used to define a search pattern for text. It is commonly used for pattern matching, validation, search and replacement, text parsing, splitting strings, etc. Java provides a powerful regex (regular expression) API through the java.util.regex package. Among the various regex patterns, \\s and \\s+ are most commonly used to handle whitespaces. 

In this blog, we will learn regex expressions (\\s and \\s+) in more detail.

Table of Contents:

• What is \\s in Java Regex?
  • Example of \\s in Java
• What is \\s+ in Java Regex?
  • Example of \\s+ in Java Regex
• Key Differences Between \\s and \\s+
• Real-life Examples of \\s vs. \\s+ in Java
  • Example1: Splitting Strings on Whitespace
  • Example2: Replacing Multiple Spaces with a Single Space
• Conclusion

What is \\s in Java Regex?

In Java, \\s is a predefined character class that matches a single whitespace character. It is used to identify and manipulate whitespace in strings, such as splitting text, trimming extra spaces, or validating input formats.

Example of \\s in Java

Code:

import java.util.regex.*;

public class Main {
    public static void main(String[] args) {
        String text = "Hello Intellipaat";
        String regex = "Hello\\sIntellipaat";
        boolean matches = Pattern.matches(regex, text);
        if(matches)
        System.out.println("Strings are same"); 
        else
          System.out.println("Strings are not same");
    }
}

Output:

Strings are same

Explanation: Here, the string text contains whitespace, while the string regex does not contain an actual whitespace but instead uses \\s to represent exactly one whitespace character in a regular expression. After that, we check whether the text matches the regex pattern using a regular expression matching function and yes, it returns that both the strings are exactly the same as expected.

What is \\s+ in Java Regex?

Unlike \\s, which matches only a single whitespace character, \\s+ matches one or more consecutive whitespace characters. The + quantifier means “one or more occurrences” of the preceding character class.

Example of \\s+ in Java Regex

Code:

import java.util.regex.*;

public class Main {
    public static void main(String[] args) {
        String text = "Hello         Intellipaat";
        String regex = "Hello\\s+Intellipaat";
        boolean matches = Pattern.matches(regex, text);
        if(matches)
        System.out.println("Strings are same"); 
        else
          System.out.println("Strings are not same");
    }
}

Output:

Strings are same

Explanation: \\s+ in “Hello\\s+Intellipaat” allows for one or more space characters, so after matching the strings it become same.

Key Differences Between \\s and \\s+

Here are the following differences between \\s and \\s+:

Real-life Examples of \\s vs. \\s+ in Java

Here are some of the real-life examples of \\s and \\s+ in Java:

Example 1: Splitting Strings on Whitespace using \\s

If you want to split a string into words containing single whitespace characters, we can consider this example:

Code:

import java.util.regex.*;
import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        String str = "Intellipaat is the best organization";
        String[] words = str.split("\\s");
        System.out.println(Arrays.toString(words));
    }
}

Output:

[Intellipaat, is, the, best, organization]

Example 2: Replacing Multiple Spaces(\\s+) with a Single Space

Code:

import java.util.regex.*;
import java.util.Arrays;
public class Main {
    public static void main(String[] args) {
        String str = "Intellipaat   is    the best   organization";
        String result = str.replaceAll("\\s+", " ");
        System.out.println(result);
    }
}

Output:

Intellipaat is the best organization

Conclusion

So far in this blog, we have learned regex expressions( \\s and \\s+) in Java. We have to use \\s, when we need to work with only one whitespace, while \\s+ is used when more than one whitespaces are required.  If you want to excel in your career in Java, please refer to our advanced Java course.

FAQs