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JDK 11 as JAVA_HOME?

Can the JAVA_HOME environment variable refer to JDK 11 (e.g. jdk-11.0.8) while running Codename One applications under Eclipse 2020-06?
Or does it need to point to JDK 8 (e.g. jdk-1.8.0_241)?
I am having the following error when I try to run Hello World app under Eclipse 2020-06 when JDK 11 is set to JAVA_HOME:
BUILD FAILED
...[shortened for brevity]...\HiWorldPrj\build.xml:106: Unable to find a javac compiler;
com.sun.tools.javac.Main is not on the classpath.
Perhaps JAVA_HOME does not point to the JDK.
It is currently set to "C:\Program Files\Java\jre1.8.0_241"
I am positive JAVA_HOME points to JDK 11 (because I can echo it from command line).
But I think I got this error because tool.jar is removed in JDK versions 9 and up and com.sun.tools.javac.Main used to be under tools.jar?

Yes you can use JDK 11 but your problem seems that the JAVA_HOME is set to the JRE and not the JDK.
Check this answer. The JRE alone cannot compile Java code.
Perhaps JAVA_HOME does not point to the JDK.
It is currently set to "C:\Program Files\Java\jre1.8.0_241"
Find where your JDK 11 directory is and set the JAVA_HOME environment variable to that path.
However I recommend that you set the Java in the Eclipse configuration tab. You'll find that at "Windows menu -> Java -> Installed JREs".
Update 1
It seems that Codename One uses JAVA_HOME, it is set up in the build.xml. So forget what I said about the Eclipse variables for now.
<property name="javaHome" value="${env.JAVA_HOME}"/>
Make sure your environment variable JAVA_HOME is set to the JDK 11. You can see dos on how to set that here.
Update 2
Also, you'll need to update every source="1.5" and target="1.5" in the build.xml file to either 1.8 or 11.
Example of the change in the eclipse.ini:
-vm
C:/Users/evand/Downloads/openjdk-11.0.2_windows-x64_bin/jdk-11.0.2/bin/javaw.exe

Your JAVA_HOME refers to the JRE, and JRE does not contain javac Java Compiler.
You need to point your JAVA_HOME environment variable to the JDK, i.e. the root directory of the Java binaries.
If your console prints the address of JDK 11 when you echo JAVA_HOME, then it might be that your IDE is configured to override that variable with the JRE directory when you're using that IDE.
Alternatively, your IDE can be using its bundled JRE, and your system might be referring to another Java binaries (JDK, in your case).

Eclipse thinks I only have Java 1.6, but when checking java-version in terminal it displays 1.7. Help :)

I just downloaded Eclipse, and it said "Version 1.7 or greater is required" for Java. Then I downloaded Java 1.7 and installed it and all that, and even restarted my computer. When I check my Java version in the terminal, it says Java 1.7, so why can't Eclipse recognize Java 1.7?
Thanks a lot! :)
My question isn't a duplicate of Running Eclipse on Mac - JVM Version 1.7 or greater is required because I installed the entire JDK 7 and my computer recognizes Java 1.7. Right now, I can't even open Eclipse.
EDIT:
current steps I have taken:
1) finding the path (/Library/Java/JavaVirtualMachines/jdk1.7.0_79.jdk/Contents/Home) to java 1.7 with command "/usr/libexec/java_home -v 1.7"
2) pasting this path by adding the following in the eclipse.ini file,
-vm
/Library/Java/JavaVirtualMachines/jdk1.7.0_79.jdk/Contents/Home
Error message is still:
Version 1.6.0_65 of the JVM is not suitable for this product. Version: 1.7 or greater is required.

I am sure you must have done this but just in case you haven't can you make sure the environment variable's are set for Java

Have you tried Window -> Preferences -> Java -> Installed JREs?
There you can add (Using the Standard VM option) a JDK (or JRE) by setting the path to the JDK install directory.

right click on
project --> properties --> java compiler
and see the jdk compiler compliance level option set to 1.7 compiler, if not change it to 1.7 or higher
EDIT :-
eclipse by default will take java installation path from %JAVA_HOME% variable, firstly you check whether you have set JAVA_HOME path in your machine.
or you can manually set java path in eclipse.ini file as said in this post
How do I set the Java path in Eclipse so I can run it on an external drive?
and
How to specify jdk path in eclipse.ini on windows 8 when path contains space

javac cannot be run, and furthermore does not seem installed

I have a problem involving setting up Java.
I have installed the JRE, added its path to PATH, and set JAVA_HOME and CLASSPATH. Now, java and javacpl work fine, but running javac generates a command-not-found error. Furthermore, javac.exe does not even seem to exist in the JRE's bin folder.
How do I run javac?

The JRE is merely the Java Runtime Environment, which includes only the infrastructure needed to run Java programs that are already compiled.
To compile Java source code using javac, you need the Java Development Kit (JDK).
On Oracle's Java download page, choose the package labelled "JDK".

In order to use javac in cmd , JDK must be installed in your system...
javac will not work if you are pointing "bin" folder inside JRE (C:\Program Files\Java**jre7**\bin)
Please check for javac.exe inside your bin folder(C:\Program Files\Java**jdk1.7.0_45**\bin)
javac.exe must be inside JDK(C:\Program Files\Java\jdk1.7.0_45\bin) not inside JRE (C:\Program Files (x86)\Java\jre7\bin) "JRE doesn't come with a compiler. It is simply a java runtime environment. What you need is the developmental kit." in order to use compiler javac
For javac path(Points to remember while setting system env variable)
path = C:\Program Files (x86)\Java\jre7\bin this is wrong
path = C:\Program Files\Java\jdk1.7.0_45\bin this is correct
Make sure "javac.exe" must be inside your "C:\Program Files\Java\jdk1.7.0_45\bin"
Dont confuse with JRE and JDK both are totally different
if you dont have JDK pls download from this link http://www.oracle.com/technetwork/java/javase/downloads/jdk7-downloads-1880260.html
reference thread for JDK VS JRE What is the difference between JDK and JRE?
Procedure:-
Install JDK
open cmd prompt
type "cd C:\Program Files\Java\jdk1.7.0_45\bin " press enter(path may change based on jdk version and 32bit and 64bit os version)
type "javac" press enter
its done
Now go and change your system environment variable
path = C:\Program Files\Java\jdk1.7.0_45\bin
this will set the path permanently

The JRE doesn't have javac - you need to download the JDK (Java Development Kit).

First, you need to install the jdk, then add the path of bin folder of jdk in the path vaiable.
you can refer to this link

Error in setting JAVA_HOME

I have recently downloaded Maven and followed the instructions given on this this page. I already have ant installed on my machine.
Now, if I want to verify that Maven is installed perfectly or not it is giving me error that JAVA_HOME is not set correctly, but same works perfectly fine for ANT.
For Maven I tried :
1. open cmd
2. type mvn -version
3. Error appeared :
C:\Users\Admin>mvn -version
ERROR: JAVA_HOME is set to an invalid directory.
JAVA_HOME = "C:\Program Files\Java\jre7\bin"
Please set the JAVA_HOME variable in your environment to match the
location of your Java installation
For ANT I tried and worked :
1. open cmd
2. type mvn -version
3. Apache Ant(TM) version 1.9.1 compiled on May 15 2013
I went to the directory to check that java.exe is actually there in that directory or not and it was there. I checked the environment variables they set fine. I restarted the system and checked again but same problem. Please let me know what am I missing.

JAVA_HOME should point to jdk directory and not to jre directory. Also JAVA_HOME should point to the home jdk directory and not to jdk/bin directory.
Assuming that you have JDK installed in your program files directory then you need to set the JAVA_HOME like this:
JAVA_HOME="C:\Program Files\Java\jdkxxx"
xxx is the jdk version
Follow this link to learn more about setting JAVA_HOME:
http://docs.oracle.com/cd/E19182-01/820-7851/inst_cli_jdk_javahome_t/index.html

Do not include bin in your JAVA_HOME env variable

Follow the instruction in here.
JAVA_HOMEshould be like this
JAVA_HOME=C:\Program Files\Java\jdk1.7.0_07

JAVA_HOME = C:\Program Files\Java\jdk(JDK version number)
Example: C:\Program Files\Java\jdk-10
And then restart you command prompt it works.

Just remember to add quotes into the path if you have a space in your path to java home.
C:\Program Files\java\javaxxx\ doesn't work
but
"C:\Program Files\java\javaxxx\" does.

The JAVA_HOME should point to the JDK home rather than the JRE home if you are going to be compiling stuff, likewise - I would try and install the JDK in a directory that doesn't include a space. Even if this is not your problem now, it can cause problems in the future!

You are pointing your JAVA_HOME to the JRE which is the Java Runtime Environment. The runtime environment doesn't have a java compiler in its bin folder.
You should download the JDK which is the Java Development Kit. Once you've installed that, you can see in your bin folder that there's a file called javac.exe. That's your compiler.

JAVA_HOME should point to jdk directory like in the image with new variable, like below
PATH should point to jdk bin like below

Run the below command in your terminal and restart it.
> set JAVA_HOME="C:\Program Files\Java\jdk-xx.xx"
xx.xx is the java version

How to set path for Jre 6 when jre 7 installed?

I am programming through java 1.6 u_17, but i have JRE version 6 and JRE version 7 installed, so how to run my compiled program from JDK 1.6 to run through the JRE 6 only?
By Default, it runs my class files through JRE 7, how to change this behavior? Any idea of setting Class path in windows 7, as we does it for JDK.
The following is shown in my command prompt
E:\JAVA>javac -version
javac 1.6.0_17
E:\JAVA>java -version
java version "1.7.0_09"
Java(TM) SE Runtime Environment (build 1.7.0_09-b05)
Java HotSpot(TM) Client VM (build 23.5-b02, mixed mode, sharing)
This is for my SET command showing the Windows 7 environment paths
ALLUSERSPROFILE=C:\ProgramData
APPDATA=C:\Users\Administrator\AppData\Roaming
ClassPath=C:\Program Files\Java\jdk1.6.0_17\bin\mysql-connector-java-5.1.5-bin.jar;
CommonProgramFiles=C:\Program Files\Common Files
COMPUTERNAME=RANDMATE-PC
ComSpec=C:\Windows\system32\cmd.exe
FP_NO_HOST_CHECK=NO
HOMEDRIVE=C:
HOMEPATH=\Users\Administrator
JAVA_HOME=C:\Program Files\Java\jre6\bin;
LOCALAPPDATA=C:\Users\Administrator\AppData\Local
LOGONSERVER=\\RANDMATE-PC
NUMBER_OF_PROCESSORS=2
OS=Windows_NT Path=C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\Program Files\Java\jdk1.6.0_17\bin;C:\Program Files\Java\jre6\bin;C:\Program Files\MyS
QL\MySQL Server 5.1\bin;C:\Program Files\UltraEdit\;C:\Program Files\Jar2Exe Wizard\;C:\Program Files\Java\jre6\bin;
PATHEXT=.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC
PROCESSOR_ARCHITECTURE=x86
PROCESSOR_IDENTIFIER=x86 Family 15 Model 6 Stepping 5, GenuineIntel
PROCESSOR_LEVEL=15
PROCESSOR_REVISION=0605
ProgramData=C:\ProgramData
ProgramFiles=C:\Program Files
PROMPT=$P$G
PSModulePath=C:\Windows\system32\WindowsPowerShell\v1.0\Modules\
PUBLIC=C:\Users\Public
SESSIONNAME=Console
SystemDrive=C:
SystemRoot=C:\Windows
TEMP=C:\Users\ADMINI~1\AppData\Local\Temp
TMP=C:\Users\ADMINI~1\AppData\Local\Temp
USERDOMAIN=RANDMATE-PC
USERNAME=Administrator
USERPROFILE=C:\Users\Administrator
windir=C:\Windows

Looks like you are using Windows. Please go the Environment Variables and define a user variable as:
Right Click(My Computers) -> Advanced -> Environment Variables -> Add
Variable Name = JAVA_HOME
Variable Value = Root Folder of Java 1.6.0_17 installation
Also in the same screen, please check the PATH variable and make sure **bin** Folder of Java 1.6.0_17 installation is added in the path preferably in the beginning and remove the Java 7 from the path, if it is there.

I fix this problem by removing the java.exe in system32 folder. And then in the cmd the java command refer to the jdk set in the path enviroment variable.

java.exe is also available in C:\windows\system32 and in your case its version might be 1.7..
Since your path has C:\windows\system32 first. no matter how to set rest of the path, sonar always will load jre7. (refer to conf\wrapper.conf in Sonar directory, by default it has wrapper.java.command=java)
To fix this, change following property of the "wrapper.conf" file
wrapper.java.command=C:\Program Files\Java\jdk1.6.0_XX\bin\java
this will fix the issue irrespective of the path variables.

For those who had the same problem I suggest reading this thread:
https://superuser.com/questions/479889/wrong-java-version-being-reported
Quote of wmz: "To check what actually executes when you run 'java -version' run from command line:
for %I in (java.exe) do #echo %~$PATH:I"

Windows is checking the PATH variable to find an executable named java and using that to launch your application. It is quite normal in a development environment to have many installations (as you do). However this calls on you to manage your environment.
There are two ways for you to set environment variables in Windows. By going to My Computer > Advanced Settings > Environment Variables as described above, you can set a variabler to your JDK installation and then update the Path to find the bin directory in that installation. Youy have the choice of updating System variables (all users) or user variables (your account only).
Personally, I prefer not to use the system/user environment variables as this provides less flexibility. You can use bat files to explicitly set the Path for a specific moment in time, or indeed to override the JAVA_HOME to point to a different installation.
If you are using an IDE you can usually specify the target runtime on a per project basis. Alternatively, when running the program, provide the fully qualified path to the version of the java executable you wish to use.

I had same problem. Issue is that Java installation will copy a java.exe, javaw.exe and javaws.exe to windows/system32 directory. You must have installed JDK7 recently.
I just removed those files from Windows/System32 directory, however, kept older version in path. This solved the issue.
Try it out.

I was facing the similar problem. I am using Java 7 and Java 8 together. The Java 8 was installed in the machine but the 7 set-up I copied from another system. I have already set the JAVA_HOME & path pointing to 7. But when I try to echo %path%, it shows the Jdk 8 in the class path. after lots of google, I have found "C:\ProgramData\Oracle\Java\javapath" in the path. Removing the line from the path solved the problem.

Background
I'm using Windows 8.1 and I have both JDK6 and JDK8 installed. For development purpose, I needed to get java version "1.6.0_45" over the command java -version and javac 1.6.0_45 over javac -version. The second command was working as expected after setting JAVA_HOME as Home folder of JDK6 and adding %JAVA_HOME/bin% in Path. However the first command was still returning java version "1.8.0_71"
Troubleshooting
I could find the an entry in the Path environment variable which points to C:\ProgramData\Oracle\Java. This folder actually contains short cut to java.exe of JDK8.
Proper solution: Uninstall JDK 8
Workaround:Edit the short cut file so that it points towards java.exe inside %JAVA_HOME%\bin (Please replace the variable with actual folder)

set the PATH variable to your jdk6\bin directory. so that it will pick the javac and java from jdk6.
for setting the path variable go to Environment Variables.
After setting the path variables you need to restart your command prompt. (NOT the computer).

Just right click on MyComputer, then Advanced System Settings-->Environment Variables-->New
Then in the "variable Name" text field add the string "PATH" or if it already exists select PATH from the list and click edit then append the path for "bin" folder in java in program files to the Variable value text field followed by a semicolon (;), if not exits add the path of bin directory of your java folder in "Variable Value" field and click "OK".
If you want to check the result, open up a command prompt and type "java" then hit enter.

For windows 7(X86) path setting:
first step:
Mycomputer(Right click)-->properties-->advanced settings-->environment variales-->new
(user variable)
on this first varible name: "" JAVA_HOME "" value: "" C:\Program Files\Java\jdk1.7.0_45 ""
second variable name: "" PATH "" value: "" C:\Program Files\Java\jdk1.7.0_45\bin;.; ""

There are two types of path for java : Permanent & Temporary.
Here is the video tutorial describing how to set path for Java?
How to Set path for Java : https://www.youtube.com/watch?v=rM4Qq3Ua7Sk
This video tutorial will guide you in setting permanent and temporary path for Java. Simply follow the steps. This will work with any version of Java, JDK or JRE. In video I have used path of JDK, Simply copy path of JRE instead of JDK and rest is same.
OR read the tutorial here : How to Set path for Java : http://aatul.me/2011/08/24/how-to-set-path-for-java/
Hope this solutions will help you.