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Editorial Team
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Asked: 2026-06-10T23:57:25+00:00

I am starting with java and I try log something. private static final Logger

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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?

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1 Answer

  1. Editorial Team

    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.

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