How do I set the default Java installation/runtime (Windows)?

Question

I\'m in the situation where I\'ve installed the JDK, but I can\'t run applets in browsers (I may not have installed the JRE).

However, when I install the JRE, it clo

Answer 1

I just had that problem (Java 1.8 vs. Java 9 on Windows 7) and my findings are:

short version

default seems to be (because of Path entry)

c:\ProgramData\Oracle\Java\javapath\java -version

select the version you want (test, use tab completing in cmd, not sure what those numbers represent), I had 2 options, see longer version for details

c:\ProgramData\Oracle\Java\javapath_target_[tab]

remove junction/link and link to your version (the one ending with 181743567 in my case for Java 8)

rmdir javapath
mklink /D javapath javapath_target_181743567

longer version:

Reinstall Java 1.8 after Java 9 didn't work. The sequence of installations was jdk1.8.0_74, jdk-9.0.4 and attempt to make Java 8 default with jdk1.8.0_162...

After jdk1.8.0_162 installation I still have

java -version
java version "9.0.4"
Java(TM) SE Runtime Environment (build 9.0.4+11)
Java HotSpot(TM) 64-Bit Server VM (build 9.0.4+11, mixed mode)

What I see in path is

Path=...;C:\ProgramData\Oracle\Java\javapath;...

So I checked what is that and I found it is a junction (link)

c:\ProgramData\Oracle\Java>dir
 Volume in drive C is OSDisk
 Volume Serial Number is DA2F-C2CC

 Directory of c:\ProgramData\Oracle\Java

2018-02-07  17:06              .
2018-02-07  17:06              ..
2018-02-08  17:08              .oracle_jre_usage
2017-08-22  11:04              installcache
2018-02-08  17:08              installcache_x64
2018-02-07  17:06         javapath [C:\ProgramData\Oracle\Java\javapath_target_185258831]
2018-02-07  17:06              javapath_target_181743567
2018-02-07  17:06              javapath_target_185258831

Those hashes doesn't ring a bell, but when I checked

c:\ProgramData\Oracle\Java\javapath_target_181743567>.\java -version
java version "1.8.0_162"
Java(TM) SE Runtime Environment (build 1.8.0_162-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.162-b12, mixed mode)

c:\ProgramData\Oracle\Java\javapath_target_185258831>.\java -version
java version "9.0.4"
Java(TM) SE Runtime Environment (build 9.0.4+11)
Java HotSpot(TM) 64-Bit Server VM (build 9.0.4+11, mixed mode)

so to make Java 8 default again I had to delete the link as described here

rmdir javapath

and recreate with Java I wanted

mklink /D javapath javapath_target_181743567

tested:

c:\ProgramData\Oracle\Java>java -version
java version "1.8.0_162"
Java(TM) SE Runtime Environment (build 1.8.0_162-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.162-b12, mixed mode)

** update (Java 10) **

With Java 10 it is similar, only javapath is in c:\Program Files (x86)\Common Files\Oracle\Java\ which is strange as I installed 64-bit IMHO

.\java -version
java version "10.0.2" 2018-07-17
Java(TM) SE Runtime Environment 18.3 (build 10.0.2+13)
Java HotSpot(TM) 64-Bit Server VM 18.3 (build 10.0.2+13, mixed mode)