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comparison doc/devel/logging.md @ 0:61d41facf527
initial v8 import (history reset)
| author | Peter Mehlitz <Peter.C.Mehlitz@nasa.gov> |
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| date | Fri, 23 Jan 2015 10:14:01 -0800 |
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| -1:000000000000 | 0:61d41facf527 |
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| 1 # The JPF Logging API # | |
| 2 There is one simple rule: do not use `System.out` or `System.err` for any permanent logging | |
| 3 | |
| 4 | |
| 5 Of course we all do this temporarily during debugging, but it really shouldn't stay in the code. The logging infrastructure is quite easy to use. Just declare a static `Logger` instance with an appropriate id (either package or logging topic) at the top of your class, and then use the `Logger` API to create output: | |
| 6 | |
| 7 ~~~~~~~~ {.java} | |
| 8 ... | |
| 9 import java.util.logging.Level; | |
| 10 import java.util.logging.Logger; | |
| 11 | |
| 12 package x.y.z; | |
| 13 | |
| 14 class MyClass .. { | |
| 15 static Logger log = JPF.getLogger("x.y.z"); | |
| 16 ... | |
| 17 log.severe("there was an error"); | |
| 18 ... | |
| 19 log.warning("there was a problem"); | |
| 20 ... | |
| 21 log.info("something FYI"); | |
| 22 ... | |
| 23 if (log.isLoggable(Level.FINE)){ // (1) don't create garbage | |
| 24 log.fine("this is some detailed info about: " + something); | |
| 25 } | |
| 26 ... | |
| 27 } | |
| 28 ~~~~~~~~ | |
| 29 | |
| 30 Note that there is only one instance for each `Logger` ID, i.e. you can have a corresponding static field in all your relevant classes, and don't have to share the fields. Another aspect that is mostly important for the lower log levels (e.g. `FINE`) is that you should't concatenate log messages in operations that occur frequently, since the corresponding `StringBuilder` instances can cause performance degradations even if the log level is not set (the arguments still get evaluated). In this case, encapsulate the logging in `log.isLoggable(level){..}` blocks. | |
| 31 |