On Windows using JDK1.4.0_01 the following occurs.

The problem is that the compiler will open all of the ZIP / JAR
files in the classpath and never close them. When you are running
the compiler standalone, it's not a problem, but when you run the
compiler in a long-running process it is. If the ZIP / JAR files do
not get closed then they are locked by the filesystem and cannot be
replaced.

In com/sun/tools/javac/v8/code/ClassReader.java, openArchive()
opens a ZipFile to the archive and stores that ZipFile object. When the
compilation is finished, the ZipFiles are never close()ed.

The classic javac compiler does not exhibit this behavior.

To recreate the problem compile Compiler2.java specifying the tools.jar in the
classpath and using java from 1.4.0 and run the Compiler2.class. This file will
compile all the java files from the jar then sleep for about 10 seconds.

At this point try moving one of the jar files to a different directory and the
following message will appear:

C:\Users\atongsch\Support\SilverStream\792653>\j2sdk1.4.0\bin\java
-classpath \j 2sdk1.4.0\lib\tools.jar;. Compiler2
Ready to Compile 2...
Status = 0
Done Compiling.
Going to Sleep.
Done Sleeping.

C:\Users\atongsch\Support\SilverStream\792653>mv ojdbc14.jar .. mv:
cannot rename "ojdbc14.jar" to "../ojdbc14.jar": The process cannot
access the file because it is being used by another process.