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After updating Java 8 (update 281) yesterday (2021-02-15) I could no longer use the Single-File Launch in the Windows Command Line. Prior to this I had no problems using this feature but now I get the following error;

Error: could not find or load main class filename.java

What did this update change or mess up? I'm very fond of the Single-File Launch feature and I would be very sad to never be able to run java files like this again. What can I do to fix this, any suggestions?

Details: I'm using the standard Windows 10 command line (cmd.exe). I have not updated the PATH variables because I don't know what to change to be honest, it worked before. Here's what I currently have in there that is relevant to Java; C:\Program Files (x86)\Common Files\Oracle\Java\javapath C:\Program Files\Java\jdk-13.0.1\bin

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    What the exact command line you are using? Did you update the Java related environment variables when you updated? Please edit the question and do not reply in the comments.
    – DavidPostill
    Commented Feb 16, 2021 at 18:11
  • According to your link, single file launch was delivered in Java 11 so if you have replaced the default Java to version 8 then launch from .java file will stop working.
    – DuncG
    Commented Feb 16, 2021 at 23:08

2 Answers 2

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It looks like you have Oracle javapath (which is probably picking Java8) before Java13 binaries which would stop the single file/compile launch working as java xyz.java.

See @DrMoishe Pippik answer for helpful info editing the path, you could try swapping the order of these directories so that Java13 is first - if that directory exists:

C:\Program Files\Java\jdk-13.0.1\bin
C:\Program Files (x86)\Common Files\Oracle\Java\javapath

But note: this may lead to a secondary issue because other apps may fail if they depend on the Java8 installation over the Java13. Confirm which default is used in CMD.EXE with:

java -version

If you want multiple JDK and have need for CMD.EXE which prefers specific JDK version you can add shortcuts to desktop with following commands:

%COMSPEC% /V /K C:\somepathtoyourbin\java8.cmd

%COMSPEC% /V /K C:\somepathtoyourbin\java13.cmd

... and add files to set the preferred JAVAHOME in java8.cmd or java13.cmd. Example java13.cmd might be:

@echo off
set "JAVAHOME=C:\Program Files\Java\jdk-13.0.1"
set "PATH=%JAVAHOME%\bin;%PATH%"
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Likely, the environment variable(s) for the path to java.exe need to be updated. First, check where java.exe and/or javaw.exe are in your PC file system. Then, open a CMD prompt, and type

echo %java_home%

or

where java

If that path is incorrect because of the update, the easiest way to correct it in Windows is with the Environment Variable editor.

  • Press Windows, type envi and select Edit the system environment variables [You must be an Administrator to do this.].
  • Select any variable with a java path that is incorrect and edit it.
  • Press Windows, type envi and select Edit environment variables for your account.
  • Select any variable with a java path that is incorrect and edit it.

You may need to reboot for the changes to take effect.

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