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JDK8 for NetBeans 12.2?

I'm trying to install JDK8 as a platform on NetBeans 12.2, but I keep getting this error message:
"Cannot detect and install the selected platform. The java or javac may not be executable."
Is there a way around this? Or is there a version of JDK8 that won't yield this error message?
Further: I should have mentioned that I'm on MACOS Big Sur.
Here's what I get with java -version in Terminal:
java version "15.0.2" 2021-01-19 Java(TM) SE Runtime Environment (build 15.0.2+7-27) Java HotSpot(TM) 64-Bit Server VM (build 15.0.2+7-27, mixed mode, sharing)
And here's what I get with javac -version:
javac 15.0.2

You are probably getting this message because the JDK executables haven't been added to your path as environment variables. Directly from the official java website, here's a guide on how to fix this problem.

Java appears to be outdated when using java -jar command

I have recently been writing some Java programs on my Windows computer. I have been trying to use java -jar to run compiled jars in order to see errors more clearly, but when I try to do this, I get the following error:
Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.UnsupportedClassVersionError: com/company/app/GUI has been compiled by a more recent version of the Java Runtime (class file version 57.0), this version of the Java Runtime only recognizes class file versions up to 52.0
This obviously means that my java version is outdated. However, when I took a look at the Java Updater, it shows that I am running the latest version.
Running java -version shows this:
java version "1.8.0_261"
Java(TM) SE Runtime Environment (build 1.8.0_261-b12)
Java HotSpot(TM) Client VM (build 25.261-b12, mixed mode)
So why is Command Prompt using an older version, and how do I change it?
Thank you for your help.

This error clearly indicates that you try to run a .jar file built with JDK 13 (major version 57) on a JRE/JDK 8 (major version 52) which is provided in PATH setting and thus invoked when running java -jar / java -version commands.
If you have JDK 13 installed on your machine, you need to check environment variable PATH and/or JAVA_HOME:
C:\Users\hp1>echo %JAVA_HOME%
C:\Java\jdk-13.0.2
C:\Users\hp1>echo %PATH%
C:\Windows\system32;C:\Java\jdk-13.0.2\bin
C:\Users\hp1>java -version
openjdk version "13.0.2" 2020-01-14
OpenJDK Runtime Environment (build 13.0.2+8)
OpenJDK 64-Bit Server VM (build 13.0.2+8, mixed mode, sharing)
If PATH refers JRE/JDK 8, you may create another variable and update PATH (copy non-java paths):
>set JAVA_13=**path_to_your_jdk_13**
>set PATH=C:\Windows\system32;%JAVA_13%\bin
If you do not have JDK 13 on your machine, to resolve this issue you should rebuild the .jar file to make it compatible with JDK 8 providing that the code is not using any features from the newer versions.

Why does my uberjar not work on Windows 7?

I created a new project using Clojure by doing this on a Mac:
lein new app clojure-noob
Created my uberjar using
lein uberjar
Sure enough, I can run this uberjar via:
java -jar target/uberjar/clojure-noob-0.1.0-SNAPSHOT-standalone.jar
And I get:
Hello, World!
Now I take this file to Windows 7 and give the same command:
java -jar clojure-noob-0.1.0-SNAPSHOT-standalone.jar
I seem to get an infinite wait. Why can’t I get to runt his .jar file on Windows?
The java version on Mac is:
java version "1.8.0_51"
Java(TM) SE Runtime Environment (build 1.8.0_51-b16)
Java HotSpot(TM) 64-Bit Server VM (build 25.51-b03, mixed mode)
The java version on Windows 7 is:
java version "1.8.0_66"
Java(TM) SE Runtime Environment (build 1.8.0_66-b18)
Java HotSpot(TM) Client VM (build 25.66-b18, mixed mode)
lein version gives the following: Leiningen 2.5.3 on Java 1.8.0_51 Java HotSpot(TM) 64-Bit Server VM

The answer is that I was trying to run the .jar from shared folders on a Windows 7 VM from VirtualBox running on a Mac. This IO is very slow.
When I just copy that file to, say, Desktop and run from there - the access is quiet fast. Thanks SubOptimal for helping me figure this out.

Error occurred during initialization of VM java/lang/NoClassDefFoundError: java/lang/Object in Redhat

I am using Redhat 6. I am in strange problem.
I was working with java 1.6. I updated my system with yum updated automatically openjdk 1.8 got install. I removed the package fro UI.
Now when I typed java -version. I get this error
Error occurred during initialization of VM
java/lang/NoClassDefFoundError: java/lang/Object.
I thought my java is corrupted and I remove java using yum remove java*. Again I installed java.
I downloaded the bin file of java 1.6 and extracted it in my home folder. edited .bash_profile and gave the path.
run .bash_profile Using . .bash_profile
Now when I type
java -version I get
java version "1.6.0_45" Java(TM) SE Runtime Environment (build
1.6.0_45-b06) Java HotSpot(TM) 64-Bit Server VM (build 20.45-b01, mixed mode)
but when i restart my system and again I type
java -version I get the same error saying
Error occurred during initialization of VM
java/lang/NoClassDefFoundError: java/lang/Object
How do i resolve it?

Eclipse launch error- error code 13

Eclipse returns this error message when launching:
I am pretty sure that both the java installation and Eclipse are both for my 64-bit system.
Here is my .ini file:

Your version of Eclipse looks OK, based on the filename.
To check your version of Java, run java -version in a console. On Windows 7 with 64-bit Java 6 I get:
java version "1.6.0_27"
Java(TM) SE Runtime Environment (build 1.6.0_27-b07)
Java HotSpot(TM) 64-Bit Server VM (build 20.2-b06, mixed mode)
Check that this is the version being used by Eclipse, as shown in your error code. If not, call that version explicitly, e.g.
"C:\Program Files (x86)\Java\jre7\bin\java.exe" -version

I moved the
-vm
up below the first openfile, not the second.
PIC: