String Utilities

import java.util.regex.Pattern;public class StringUtils {    private static final Pattern EMAIL_PATTERN =         Pattern.compile("^[A-Za-z0-9+_.-]+@[A-Za-z0-9.-]+$");        public static boolean isValidEmail(String email) {        return email != null && EMAIL_PATTERN.matcher(email).matches();    }        public static String toCamelCase(String str) {        if (str == null || str.isEmpty()) return str;                String[] parts = str.split("[-_\\s]+");        StringBuilder result = new StringBuilder(parts[0].toLowerCase());                for (int i = 1; i < parts.length; i++) {            if (!parts[i].isEmpty()) {                result.append(Character.toUpperCase(parts[i].charAt(0)));                result.append(parts[i].substring(1).toLowerCase());            }        }        return result.toString();    }        public static String truncate(String str, int maxLength, String suffix) {        if (str == null || str.length() <= maxLength) return str;        return str.substring(0, maxLength - suffix.length()) + suffix;    }        public static String padLeft(String str, int length, char padChar) {        if (str == null) str = "";        if (str.length() >= length) return str;        return String.valueOf(padChar).repeat(length - str.length()) + str;    }}

import static StringUtils.*;public class Example {    public static void main(String[] args) {        String email = "[email protected]";        System.out.println("Email valid: " + isValidEmail(email));                String input = "hello-world-example";        System.out.println("Camel case: " + toCamelCase(input));                String text = "This is a very long string that needs truncation";        System.out.println("Truncated: " + truncate(text, 20, "..."));                String number = "42";        System.out.println("Padded: " + padLeft(number, 5, '0'));    }}