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how to delete java completely from windows

I have messed up my windows java installation and i want to delete everything and re-install java , all of my java versions have been messed up and I don't know what to do in this situation
when I do:
C:\Users\LENOVO>echo %JAVA_HOME%
C:\Program Files\Java\jdk-17.0.1
C:\Users\LENOVO>javac -version
javac 17.0.1
C:\Users\LENOVO>java -version
java version "1.8.0_311"
Java(TM) SE Runtime Environment (build 1.8.0_311-b11)
Java HotSpot(TM) Client VM (build 25.311-b11, mixed mode, sharing)
Why is java -version showing different things?
I HAVE TRIED CHANGING PATH AND THERE IS NOTHING IN MY PATH RELATED TO JAVA 1.8.0.
I TRIED MANUALLY DELETING JAVA BUT IT ALWAYS SAID IT IS OPEN SOMEWHERE ELSE AND CLOSE THAT BEFORE MAKING ANY CHANGES HERE

first of all you must go environment variables and then delete all Java related paths and after that follow those links and delete them also from your local computer. It's done :)

I'm not sure how to fix the issue regarding it being open elsewhere but I'd recommend trying to open task manager to close Java that way.
As for uninstalling it, you can uninstall it as it is an app. Just open settings, go to apps, search Java, and uninstall it like so.

How to install openJdk 8 in windows 64 bit os

I need to install open JDK in my Windows 64-bit os. I have used ORACLE open JDK and downloaded from the below link: https://jdk.java.net/8/
While downloading I have selected Accept License Agreement and installed.
But, after the installation when I tried checking the version using command java -version it's showing like regular JDK.
Can anyone help me to get where I went wrong? Or is there any better vendor to install open JDK in windows. Thanks.

Amazon offers an open jdk for Windows (and other OS), but just for Java 8, 11 and 16.
You can download it from here: https://aws.amazon.com/es/corretto/
After installing it and running the java -version command, you will see something like this:
>java -version
openjdk version "1.8.0_242"
OpenJDK Runtime Environment Corretto-8.242.08.1 (build 1.8.0_242-b08)
OpenJDK 64-Bit Server VM Corretto-8.242.08.1 (build 25.242-b08, mixed mode)

You need to set your java version in environment of you machine and target your JDK8 bin folder, or any JDK that you want to have at your disposal when you run java -version.

The best way to do this is to use the builds from adoptopenjdk. They're very high quality and come in multiple variants for Windows ranging from zip files to MSI installers. Dead simple to install JDK 8, 11 or 15.
But, after the installation when I tried checking the version using command java -version it's showing like regular JDK.
This is because JAVA_HOME is pointing to your old JDK. You need to go to Control Panel and change the Environment Variables. Just do a search on Windows 10 for "Environment Variables" to easily find that configuration panel.

Azul Systems provides builds of OpenJDK and relative installers, for all OSes and JDK versions.
It also provides builds of the JDK with OpenJFX included.
The installers bind JAR files to be executed by Java on Windows.
Download from azul.com website

I know this is old but should anyone run across this in search of OpenJDK 8 go here
https://developers.redhat.com/products/openjdk/download

Cannot use Java 7 installation if Java 8 is installed

I normally still use Java 7 for all my coding projects (it's a company "politics" issue), but I installed Java 8 for one third-party project I am contributing to. Now, it seems I cannot have Java 8 installed in Windows 7 x64, and still use Java 7 by default:
C:\>"%JAVA_HOME%\bin\java.exe" -version
java version "1.7.0_55"
Java(TM) SE Runtime Environment (build 1.7.0_55-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.55-b03, mixed mode)
C:\>java.exe -version
java version "1.8.0_05"
Java(TM) SE Runtime Environment (build 1.8.0_05-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.5-b02, mixed mode)
As you can see, JAVA_HOME is completely ignored.
I also have Java in the path, using "%JAVA_HOME%\bin", which resolve correctly to Java 7 when I check the path in a DOS box, but it still makes no difference.
I checked in the "Java Control Panel" (not sure if this affects the default command-line Java version). Under the "Java" tab, the "View..." button, you get to see "registered" Java versions. I can add all the versions under the "User" tab, but under "System" there is only Java 8, and no way to change it.
Am I missing something, or did Oracle just make it impossible to use Java 7, unless I de-install Java 8? I don't want to have to specify the "source" and "target" everywhere, and I don't even know if it is possible for me to specify it everywhere, where Java is used.
EDIT: What I did is I de-installed all Java. Then installed the latest Java7 (both 86 and x64), and then the latest Java8 (both 86 and x64). After I did that, I noticed that the x64 JDK was gone. It seems Java8 killed it. So I re-installed the JDK 7 x64, after the JDK 8 x64. Still, JDK7 x64 did not seem to "replace" the "java.exe" which is copied into the "Windows" directory itself (I assume THAT is the problem).

When you install jdk8 it adds an entry like this
C:\ProgramData\Oracle\Java\javapath
to beginning of your PATH environment variable, removing this entry should resolve your problem.

You can select the JRE version from the command line with the -version: option.
> java -version:"1.7" MyClass
should select the 1.7 JRE if installed properly.
The list of the properly installed JRE is in the registry, see the key :
HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment (32bit)
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\JavaSoft\Java Runtime Environment (64bit)
You can set the "CurrentVersion" there if you want a different default version than the latest.
See http://docs.oracle.com/javase/7/docs/technotes/tools/windows/java.html#options
Don't modify your PATH to point to a particuliar JRE, let the special java.exe in Windows/system32 do the job.

Windows and Unix both find programs using their PATH environment variable. You have an java.exe in your Windows\System32 which is appearing before your "preferred" version of Java.
Change the PATH to be the one you need, or specify the full path when you need a different version.

2 Steps
1
Change registry key **HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment\CurrentVersion** to point to 1.7
2
Copy java.exe,javaw.exe and javaws.exe from your java 1.7 version to Windows\System32 folder
(Since the corresponding files of java 1.8 are already there, you might have to overwrite with admin permissions)
3
(OOps actually not required 3rd step )
Open a new cmd window and check
java -version

Looks like you have to check where in your PATH is located your JAVA_HOME variable, the PATH is evaluated from left to right. A tip for you is to do all your Java system variables configuration at the beginning of your PATH.
PATH = %M2_HOME%\bin;%JAVA_HOME%\bin;C:\ProgramData\Oracle\Java\javapath;...
Probably that's why after doing this:
- java -version
you are getting this:
- java version "1.8.0_05"
because there are other areas in your PATH that are pointing to other java.exe, for example C:\Windows\System32 or C:\ProgramData\Oracle\Java\javapath etc.

I had to make 2 changes for it to work:
Changed the Registry key 'Software\JavaSoft\Java Runtime Environment'\CurrentVersion' to 1.7 from 1.8
The Java 8 installation adds a new entry to the PATH environment variable 'C:\ProgramData\Oracle\Java\javapath'. I removed this entry from the PATH.

Java runtime environment error

This may seem trivial but I haven't been able to find a fix.
I've installed the latest Java runtime environment but when I run java -version on the command line, I still get Java(TM) SE Runtime Environment (build 1.7.0_40-b43)
However, when I test my Java version in browser, it works fine.
How can I get Terminal using the latest java version?

see Installed Java 7 on Mac OS X but Terminal is still using version 6
maybe you need to select the java version you want to see.

I am assuming you are using windows..
from your command line
echo %PATH%
make sure your java PATH is pointing your latest java bin folder.
I am not sure about the Mac but Can you verify if you have symlink setup under /usr/bin?
ex. /usr/bin/java -> java_path
Maybe you can change this symlink to point to the latest java you have installed.

Why doesn't netbeans 7.3 see that I've installed Java 1.7.0_21?

I've recently installed netbeans 7.3 on my Mac (Lion 10.7.5, up-to-date).
At the command line, I would get:
[129]$java -version
java version "1.6.0_45"
Java(TM) SE Runtime Environment (build 1.6.0_45-b06-451-11M4406)
Java HotSpot(TM) 64-Bit Server VM (build 20.45-b01-451, mixed mode)
Today I went to the netbeans plugin window and found 18 updates to install. When I attempted to do this, I received a message that some of them require > Java 1.7, and I only have 1.6 (as indicated above). So I dutifully ran out to java.com and downloaded Java 1.7 Update 21 successfully.
When I run a Java version checker in various browsers I see a report that Java 1.7.0_21 is the installed version. In addition, the Mac's Java Control Panel also indicates that 1.7.0_21-b12 is the current version.
However, upon restarting netbeans, it still has the same complaint that Java 1.6 is in use. I've rebooted the machine and get the same result. And, the result of 'java -version' at the command line also still shows the same result as above (1.6.0_45).
And, finally, even if I try something like:
/usr/libexec/java_home -v 1.7.0_21 --exec java -version
I get:
Unable to find any JVMs matching version "1.7.0_21"
I'm baffled. Does anybody have any advice on this?
Thanks.
Doug

netbeans will be using it's own version of the the JDK try this
where-can-i-set-the-jre-jdk-which-is-used-to-run-netbeans-besides-the-command-line