Java Programming

This is the stack trace, I am using log4j1.2.12, I checked source code of log4j, I found it finally call System.out.write!

What's the matter? This problem happened yesterday, and it happened several times in several programs during 6 months.

Thanks!!

java.lang.Thread.State: RUNNABLE
at java.io.FileOutputStream.writeBytes(Native Method)
at java.io.FileOutputStream.write(FileOutputStream.java:260)
at java.io.BufferedOutputStream.write(BufferedOutputStream.java:105)
- locked <0x94c0d618> (a java.io.BufferedOutputStream)
at java.io.PrintStream.write(PrintStream.java:430)
- locked <0x94c0d5f8> (a java.io.PrintStream)
at org.apache.log4j.ConsoleAppender$SystemOutStream.write(ConsoleAppender.java:173)
at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:202)
at sun.nio.cs.StreamEncoder.implFlushBuffer(StreamEncoder.java:272)
at sun.nio.cs.StreamEncoder.implFlush(StreamEncoder.java:276)
at sun.nio.cs.StreamEncoder.flush(StreamEncoder.java:122)
- locked <0x94c707a8> (a java.io.OutputStreamWriter)
at java.io.OutputStreamWriter.flush(OutputStreamWriter.java:212)
at org.apache.log4j.helpers.QuietWriter.flush(QuietWriter.java:57)
at org.apache.log4j.WriterAppender.subAppend(WriterAppender.java:315)
at org.apache.log4j.WriterAppender.append(WriterAppender.java:159)
at org.apache.log4j.AppenderSkeleton.doAppend(AppenderSkeleton.java:230)
- locked <0x94c6ff68> (a org.apache.log4j.ConsoleAppender)
at org.apache.log4j.helpers.AppenderAttachableImpl.appendLoopOnAppenders(AppenderAttachableImpl.java:65)
at org.apache.log4j.Category.callAppenders(Category.java:203)
- locked <0x94c75240> (a org.apache.log4j.Logger)
at org.apache.log4j.Category.forcedLog(Category.java:388)
at org.apache.log4j.Category.log(Category.java:853)
at org.apache.commons.logging.impl.Log4JLogger.info(Log4JLogger.java:193)