Print first letter of each word in a string using regex

Given a string, the task is to extract and print the first letter of each word using a regular expression. Here, a word is considered a sequence of English alphabetic characters (a-z or A-Z). The regular expression \b[a-zA-Z] can be used to find the first alphabetic character at each word boundary.

• Java requires \\b instead of \b inside a string literal.
• Matcher.find() is used to locate each occurrence.

Illustration

Input: "Geeks for geeks"
Output: Gfg

Input: "United Kingdom"
Output: UK

How It Works

• \b represents a word boundary.
• [a-zA-Z] matches one uppercase or lowercase English letter.
• Together, \b[a-zA-Z] matches the first letter of each word.
• In a Java string literal, \b must be written as \\b because the backslash must be escaped.

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class GFG {

    public static void main(String[] args) {

        String str = "Geeks for Geeks";

        // Create regex pattern to match the first
        // letter of each word
        Pattern pattern = Pattern.compile("\\b[a-zA-Z]");

        // Create Matcher for the input string
        Matcher matcher = pattern.matcher(str);

        System.out.print("First letters: ");

        // Find and print the first letter of each word
        while (matcher.find()) {
            System.out.print(matcher.group());
        }
    }
}

First letters: GfG

Explanation

• Pattern.compile("\\b[a-zA-Z]") creates the regular expression pattern.
• pattern.matcher(str) creates a Matcher for the given string.
• matcher.find() searches for the next matching first letter.
• matcher.group() returns the matched character.
• The loop continues until all word-start letters are found.