I am using log4j as a logging API (essentially for debugging purpose) at work and I was thinking of using it for my game dev too. I can''t remember the URL but maybe you should go there to have an idea of which sort of API I am talking here : http://www.apache.org/jakarta Anyway, as the problem with Java game programming is mostly speed, I just wanted to know if you guys were using any logging API for your game dev debugging or have any opinion about the subject. An easy solution would be to code it with debug statements and then remove them for the final release but then we would have some speed difference. Also, I think logging would be useful even in the final release in order to identify bugs. And during the beta stage we need debbuging statements AND actual release speed. Anyone has an opinion ?

In my experience, logging libraries aren''t really worth it. I tend to just write my own static log(String toLog) method in some class, then just make it return when I don''t want to log any more.

Then again, if you''re working on a huge project with several coders, log4j is probably as good as they come.

log4j may also be more useful if your using client/server software and want the client to log back to the server. A simple System.out.println doesn''t cut it anymore in that situation.

Why not? Just make it send the log-message to the server, and add a LOGMSG or something to the protocol.

Of if you''re using RMI, it''s even easier.

I think abstracting out logging into an interface or abstract class does have merit. This allows you to change the logging implementation without affecting any of your code. log4J may
be a bit of overkill for a gaming project, try something like
this:

abtract public class Log {

static private Log singleton;

static {
//static initializer to setup the singelton.

//You can specify which implementation of the logging you
//want.
String lClassName = System.getProperty("LogClass");

//Default the implementation if not specified on the
//commandline.
if (lLogName == null)
lClassName = "com.foo.LogStdOut";

try {
LogClass = Class.forName (lClassName);
singleton = (Log) logClass.newInstance ();
} catch (Exception pException) {
System.out.println ("Could initialize logging.");
}
}

static void logMessage(String lChannel, String lMessage) {
singleton.logMessageImpl(lChannel, lMessage);
}

abstract protected void logMessageImpl(String lChannel,
String lMessage);
}


Now create an implementation:

public class LogStdOut extends Log {
protected void logMessageImpl(String lCode, String lMessage) {
System.out.println(lMessage);
}
}

OR

public class LogToServer extends Log {
protected void logMessageImpl(String lCode, String lMessage) {
//Code to send message to server.
}
}


Finally, if you are really concerned about CPU cycles, you
can get a psuedo "#define"

public class Debug {
public static final boolean DEBUG = true;
}

Just wrap any calls to logging with :

if (Debug.DEBUG)
Log.logMessage("DEBUG", "Debug message.");

The compiler with optimize out the "if" statement AND your log
message if the boolean "DEBUG" is set to false. Keep in mind this
happens at compile time.

If you need the ability to turn debugging on and off, remove
the "final" keyword from the boolean and recompile everything.

If your interested, create an example, compile the file, and
use JAD to decompile. It gives you a good idea of what is going
on beneath the covers.


Tyler.

Thanks a lot !
I think I will start coding my own minimalist Logging API this way. The thing you say with the #define-like statements means that the code can behave just like if you removed the log statements in the final release. Sounds good to me when looking for maximum speed.

Herve.

Tyler,

I recently asked a Sun java engeneer that exactq question and he said definatly that a seperate Debug.DEBUG would not work at compile time and it would have to resolv at runtime.

Are you sure that works outside of the scope of one class?

Snowmoon,

I just compiled a little test to verify:

Debug.java:
=========================================================
public class Debug {

/** Debug flag. **/
public static final boolean DEBUG = false;
}

Test.java :
=========================================================
public class Test {

public Test() {
}

public static void main(String[] args) {

if (Debug.DEBUG) {
System.out.println("Foo");
}
}
}

I compiled both classes using Jbuilder''s compiler and
I used Jad to decompile Test.class back into source and this
is what resulted:

/**
* Intr@byte ©2000 by 3logie.com
* WARNING: Intr@byte is only provide for ofuscator test purposes
* Please apply the author''s licence
*/
// Source File Name: Test.java


public class Test
{

public Test()
{
}

public static void main(String args1[])
{
}
}

I also tried it with javac and this is what jad produced:

/**
* Intr@byte ©2000 by 3logie.com
* WARNING: Intr@byte is only provide for ofuscator test purposes
* Please apply the author''s licence
*/
// Source File Name: Test.java


public class Test
{

public Test()
{
}

public static void main(String args[])
{
}
}

It appears to be working, although maybe there are subtle things that I am not aware of.

Tyler.