Regex expressions in Java, s vs. splus

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.

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