Files left in directory after running javac for JDK1.8

If I run

javac File.java

and run ls, what's left is

129161 File.class File.java

file 129161
129161: data

ls -l
32768 Jul 24 20:41 129161
 1493 Jul 24 20:53 File.class
 1018 Jul 23 16:08 File.java

The files obviously a binary, but the first couple of lines include:

@J8sun.rt._sync_EmptyNotifications8J0sun.rt._sync_NotificationsJ8sun.rt._sync_ContendedLockAttempts8J0sun.rt._sync_FutileWakeups0J(sun.rt._sync_Parks
                                                               8J0sun.rt._sync_SlowEnter8J0sun.rt._sync_SlowExit8J0sun.rt._sync_SlowNotify8J0sun.rt._sync_SlowNotifyAll8J0sun.rt._sync_FailedS

Can anyone explain or reference documentation of exactly why the strangely number files are created in this directory every time I run javac.

For the record, I only see this with versions of oracle JDK 1.8.

I found this on the chineese version of the web site as it says,You may have placed these files in the usual temporary directories of the development system.

The search for a few symbols in the "readable" line seems to point to the hsperfdata artifact. See this hsperfdata Github parsing project. After exiting, it is possible to safely delete them. Java

Note: If these are hsperfdata components, the numbers are process identifiers. You may have placed these files in the usual temporary directories of the development system.

(The initial assumption is that the remaining files may be class file artifacts extracted from deleted JAR files.)

When you compile a java file as: javac File.java(enter) then .class file is generated which is java byte code, which is the instruction set of the Java virtual machine (JVM) to interpret your code.