A Regex (Regular Expression) serves to specify a search pattern for text. It is frequently utilized for pattern identification, validation, searching and substitution, text interpretation, string division, and more. Java includes a robust regex (regular expression) API via the java.util.regex package. Among the various regex patterns, s and s+ are the most widely employed to manage whitespaces.

In this article, we shall explore regex expressions (s and s+) in greater depth.

Table of Contents:

• What does s mean in Java Regex?
  • Illustration of s in Java
• What does s+ signify in Java Regex?
  • Illustration of s+ in Java Regex
• Primary Differences Between s and s+
• Practical Examples of s versus s+ in Java
  • Example 1: Dividing Strings by Whitespace
  • Example 2: Substituting Multiple Spaces with a Solo Space
• Wrap-Up

What does s mean in Java Regex?

In Java, s is a built-in character class that corresponds to a single whitespace character. It is utilized to recognize and manipulate whitespace within strings, for instance, separating text, trimming unnecessary spaces, or validating input formats.

Illustration of s in Java

Code:

import java.util.regex.*;

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

Result:

Strings are equivalent

Explanation: In this case, the text string has whitespace, while the regex string does not actually include a whitespace but instead represents one whitespace character in a regular expression through s. Following this, we verify if the text aligns with the regex pattern using a regex matching function, and indeed, it confirms that both strings are precisely equivalent to what was anticipated.

What does s+ signify in Java Regex?

In contrast to s, which identifies solely one whitespace character, s+ corresponds to one or more contiguous whitespace characters. The + quantifier indicates “one or more instances” of the preceding character class.

Illustration 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 = "Hellos+Intellipaat";
        boolean matches = Pattern.matches(regex, text);
        if(matches)
        System.out.println("Strings are equivalent"); 
        else
          System.out.println("Strings are not equivalent");
    }
}

Result:

Strings are equivalent

Explanation: The s+ in “Hellos+Intellipaat” permits one or more whitespace characters, allowing the strings to match and thus become equivalent.

Primary Differences Between s and s+

Below are the distinctions between s and s+:

Regex	Definition
s	Matches only a single whitespace character.
s+	Matches multiple whitespace characters.

Practical Examples of s versus s+ in Java

Here are some real-world applications of s and s+ in Java:

Example 1: Dividing Strings by Whitespace using s

If you wish to separate a string into words using single whitespace characters, consider the following 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));
    }
}

Result:

[Intellipaat, is, the, best, organization]

Example 2: Substituting Multiple Spaces(s+) with a Solo 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);
    }
}

Result:

Intellipaat is the best organization

Wrap-Up

In this article, we have examined regex expressions (s and s+) in Java. Use s when working with a single whitespace, while s+ is necessary when you require one or more whitespaces. If you aspire to advance your career in Java, please check out our advanced Java course.

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