import java.util.regex.Matcher;

import java.util.regex.Pattern;

public class LogValidator {

/**

* Validates a log entry against a set of constraints.

* @param logEntry The log entry string to validate.

* @param usernameRegex Regular expression for username validation.

* @param logLevelRegex Regular expression for log level validation.

* @param messageLength The maximum length of the log message.

* @return True if the log entry is valid, false otherwise.

*/

public static boolean isValidLogEntry(String logEntry, String usernameRegex, String logLevelRegex, int messageLength) {

// Validate username format

Pattern usernamePattern = Pattern.compile(usernameRegex);

Matcher usernameMatcher = usernamePattern.matcher(logEntry);

if (!usernameMatcher.find()) {

System.out.println("Invalid username format.");

return false;

}

// Validate log level

Pattern logLevelPattern = Pattern.compile(logLevelRegex);

Matcher logLevelMatcher = logLevelPattern.matcher(logEntry);

if (!logLevelMatcher.find()) {

System.out.println("Invalid log level format.");

return false;

}

// Validate message length

if (logEntry.length() > messageLength) {

System.out.println("Message exceeds maximum length.");

return false;

}

// Add more constraints here as needed

return true;

}

public static void main(String[] args) {

// Example usage

String logEntry1 = "user123 [INFO] This is a valid log message.";

String logEntry2 = "invalid-user [ERROR] Short";

String logEntry3 = "user456 [DEBUG] This is a very long log message that exceeds the maximum allowed length.";

String usernameRegex = "^[a-zA-Z0-9]+$"; // Example username regex

String logLevelRegex = "^(DEBUG|INFO|WARN|ERROR|FATAL)$"; // Example log level regex

int messageLength = 100; // Example message length limit

System.out.println("Log Entry 1 is valid: " + isValidLogEntry(logEntry1, usernameRegex, logLevelRegex, messageLength));

System.out.println("Log Entry 2 is valid: " + isValidLogEntry(logEntry2, usernameRegex, logLevelRegex, messageLength));

System.out.println("Log Entry 3 is valid: " + isValidLogEntry(logEntry3, usernameRegex, logLevelRegex, messageLength));

}

}