How java 8 lambda lazy evaluation helps in clean logging code.

The tradition way of logging was to check for a specific level of Log Level and then perform some activity

if(log.isDebugEnabled()){
log.debug("log debug is ", () -> getMessage());
}

Apache logger 2.4 and above supports Lambda expression which can benefit from the lazy evaluation, hence making the if() check unnecessary.

• If the loglevel is not debug then getMessage() function will not be called as lambda functions are evaluated lazy

<dependencies>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-api</artifactId>
        <version>2.8.1</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-core</artifactId>
        <version>2.8.1</version>
    </dependency>
</dependencies>


[addToAppearHere]

import org.apache.logging.log4j.LogManager;

import java.util.UUID;

public class Logger {

    public static String getMessage() {
        return UUID.randomUUID().toString();
    }

    public static final org.apache.logging.log4j.Logger log = LogManager.getLogger(Logger.class);

    public static void main(String[] args) {

        log.debug("log debug is ", () -> getMessage());
    }
}