When creating a program in Java, we are mostly, if not always, add logging mechanism in our program. This log can be use to add debug information to our program, which can help us when problem occurs in our program. We usually add log message to the start of our methods to show the value of input parameters, or at the end of the methods before exiting to show the process results. We also add log information in the catch block of the try-catch statement to log messages related to exception that occurs in our program.

Here’s an example to illustrate the difference:

Concatenation approach:

logger.info("User " + username + " logged in at " + loginTime);

Parameterized approach:

logger.info("User {} logged in at {}", username, loginTime);

In Java, using parameterized log messages instead of concatenation offers several benefits:

Performance

Parameterized log messages can improve performance compared to string concatenation. When you concatenate strings, the JVM creates a new string object each time, which can lead to unnecessary memory allocation and garbage collection overhead. Parameterized messages, on the other hand, only evaluate the placeholders when the log message is actually logged, which can reduce memory usage and improve performance.

Readability

Parameterized log messages often result in cleaner and more readable code. By separating the log message template from the actual values, it’s easier to understand the intent of the log message and identify the dynamic values being logged.

Internationalization (i18n) and Localization (l10n)

Parameterized log messages make it easier to support internationalization and localization efforts. Since the placeholders in the log message template remain the same regardless of the language, translators can focus solely on translating the template and not worry about the dynamic values.

Prevention of unnecessary string manipulation

When concatenating strings for log messages, you may inadvertently perform unnecessary string manipulation operations (e.g., converting non-string values to strings). With parameterized messages, these operations are only performed if the log message is actually logged, reducing unnecessary computation.

Avoidance of potential formatting issues

When concatenating strings, you may encounter formatting issues, especially if the dynamic values contain special characters or formatting codes. Parameterized messages handle formatting automatically, ensuring that the logged values are properly formatted according to their data types.

Overall, using parameterized log messages can lead to more efficient, readable, and maintainable code in Java logging practices.

Below is another ilustration of adding log messages in our program:

package org.kodejava.util.logging;

import java.util.logging.Level;
import java.util.logging.Logger;

public class ExampleLogger {

    private static final Logger logger = Logger.getLogger(ExampleLogger.class.getName());

    public void performLogin(String username, String loginTime) {
        // Simulate login process
        boolean loginSuccessful = true; // Assume login is successful for demonstration

        if (loginSuccessful) {
            // Log successful login using parameterized message
            logger.log(Level.INFO, "User {0} logged in at {1}", new Object[]{username, loginTime});
        } else {
            // Log failed login using parameterized message
            logger.log(Level.WARNING, "Failed login attempt for user {0} at {1}", new Object[]{username, loginTime});
        }
    }

    public static void main(String[] args) {
        ExampleLogger exampleLogger = new ExampleLogger();
        exampleLogger.performLogin("john_doe", "2024-06-08 10:00:00");
    }
}

In this example:

• We define a performLogin method that simulates a user login process. The method takes username and loginTime as parameters.
• Inside the method, we set a boolean variable loginSuccessful to true for demonstration purposes (assuming the login is successful).
• We then use the java.util.logging.Logger class to log the login event. We use parameterized log messages with placeholders {0} and {1} for username and loginTime, respectively.
• Depending on whether the login is successful or not, we log the event at different levels (INFO for successful login and WARNING for failed login).
• In the main method, we create an instance of ExampleLogger and call the performLogin method with sample values for username and loginTime.

This example demonstrates the usage of parameterized log messages in a complete method for logging login events in Java.