Java Logger - Netbeans hint "Inefficient use of string concatenation in logger"

Question

I am starting with java and I try log something.

private static final Logger _logger = Logger.getLogger("my"); 

String car = "bmw";
String dog = "dog"; 

_logger.info(car + " text " + dog); // on this line Netbeans

.. on this line Netbeans show me yellow bulb and say: Inefficient use of string concatenation in logger

So I click on "Convert string concatenation to a message template" and it change code to:

_logger.log(Level.INFO, "[{0}] v{1} enabled", new Object[]{car, dog});

That cause problem. Because in log I see: [{0}] v{1} enabled How to fix it?

Answer 1

You have a few options

1) Use String.format() _logger.log(Level.INFO, String.format("[%s] %s enabled", car, dog)).

2) Use StringBuilder.append() or String.concat()`.

Ex: _logger.log(Level.INFO, new StrinBuilder(car).append(" text ").append(dog));

This is essentially what javac does in optimization.

3) Ignore the warning because efficiency is irrelevant for this. If you really cared about speed, you wouldn't be logging things. Logging takes a long time, and the difference between String formatting and String appending is very small relative to the time spent writing the log.

Answer 2

It's just helping advice from Netbeans, actually code

_logger.info(car + " text " + dog); // on this line Netbeans
_logger.log(Level.INFO, "{0} text {1}", new Object[]{car, dog});

produce the same output. The first variant more coder friendly less time for typing debug messages, the second awesome.

Answer 3

Any approach that generates the de-parameterized string before determining whether the message should be written is inefficient.

You probably have a poorly written java.util.logging.Formatter. By that, I mean a formatter that simply output's LogRecord.getMessage() instead of incorporating LogRecord.getParameters()