I recently downloaded an early access release of JDK 9 (build 68) for my Windows 7-based laptop. Because this is an early release, I was not surprised when the automatic installation introduced some less than ideal issues with the main Java Runtime Environment (JRE) installation on my laptop. After playing with the JDK 9 features that I wanted to try out, I downloaded the latest Oracle JDK 8 (Update 45) and used the automatic installer to install that. While still in that session, everything worked well.
When I powered up the laptop and logged in the next morning, my Java runtime environment was not healthy. The problem traced to specification of
C:\ProgramData\Oracle\Java\javapath\java.exe as the first entry in my
Path environment variable. When I changed directories to see the contents of the
C:\ProgramData\Oracle\Java\javapath directory, I saw the following:
This screen snapshot indicates that the
javaws.exe entries in the
C:\ProgramData\Oracle\Java\javapath\ directory are actually symbolic links (
<SYMLINK>) to similarly named executables in the JRE 9 installation.
The next screen snapshot shows the effect of this on my Java runtime environment:
The message is very clear on what the issue is: "The system cannot find the file C:\ProgramData\Oracle\Java\javapath\java.exe." The reason that the system is looking for that is because the
C:\ProgramData\Oracle\Java\javapath\ directory is the first entry in the
Path and the symbolic links in that directory point to a JRE 9 directory that doesn't exist (I only have the JDK 9 directory):
StackOverflow user shpeley provides a nice overview of this situation and how he/she solved it. As I did, shpeley found that the automatic installer did not update these symbolic links when moving back versions (in shpeley's case, from JDK 8 to JDK 7). Borrowing from shpeley's solution (convenient because the syntax for making symbolic links in DOS is provided), I ran the following commands in the
mklink java.exe "C:\Program Files\Java\jdk1.8.0_45\bin\java.exe" mklink javaw.exe "C:\Program Files\Java\jdk1.8.0_45\bin\javaw.exe" mklink javaws.exe "C:\Program Files\Java\jdk1.8.0_45\bin\javaws.exe"
The Oracle JDK/JRE installation on Windows normally goes very smoothly and, at most, I typically only need to change my
%JAVA_HOME% environment variable to point to the new directory (when upgrading the JDK). However, when things occassionally don't go as smoothly, it's helpful to be aware of the directory
C:\ProgramData\Oracle\Java\javapath\ and its symbolic links. In (fortunately rare) cases, it may even be necessary to change these symbolic links.
UPDATE: Ganesh's comment reminded me that it may be necessary to run Command Prompt (or Powershell) as Administrator to perform the operations discussed in this post. Two screen snapshots that follow demonstrate doing this in Windows 10. The first image shows right-clicking on "Command Prompt" and selecting "Run as administrator" and the second image shows what a Command Prompt window opened in that fashion looks like (in this case, it says "Administrator: Command Prompt" in the window's title bar rather than the normal "Command Prompt".