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WSL Bash isn't finding java in PATH

I have an export command in my .bashrc to add the path of the java.exe file to PATH. Right now, running echo $PATH gives me this at the end
/mnt/c/Program Files/Java/jdk-14.0.2/bin
This is exactly where the java.exe and javac.exe files are stored, but when I run something like
java -version I'm getting the Command 'java' not found error. What am I doing wrong here?

You have added the Windows version of the Java binaries to the Path. You use WSL to run Linux binaries. (WSL1 is a compatibility layer, WSL2 uses the Linux kernel).
You have two options:
Install Java in your WSL environment. For example on Ubuntu with following commands:
sudo apt update
sudo apt install openjdk-14-jdk
After installing Java it will be available in the search path.
You could also run the Windows version by calling java.exe (note the .exe) on the name. This way WSL would call the Windows version. (https://learn.microsoft.com/en-us/windows/wsl/interop#run-windows-tools-from-linux)

If you want to use the windows version of java for some reason you where almost there. Try this please :)
java.exe -version

Install java in wsl:
sudo apt-get -y install openjdk-14-jdk
check the version.
java –version
check the path to config JAVA_HOME.
sudo update-alternatives --config java
eg
/usr/lib/jvm/java-14-openjdk-amd64/bin/java.
edit environment file to add the path:
sudo nano /etc/environment
add declare and add the JAVA_HOME:
PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:$JAVA_HOME/bin"
JAVA_HOME=/usr/lib/jvm/java-14-openjdk-amd64
save and check the path.
source /etc/environment
echo $JAVA_HOME
Output
/usr/lib/jvm/java-14-openjdk-amd64

Java default packages

I write a small java program to read file and do the string matching in windows 8 by using net beans. But when i compile it on ubuntu by using terminal following message appeared. Is there any default packages in ubuntu , for following packages in the error.
The program 'javac' can be found in the following packages:
* default-jdk
* ecj
* gcj-4.6-jdk
* gcj-4.7-jdk
* openjdk-7-jdk
* openjdk-6-jdk
Try: sudo apt-get install <selected package>
ucsc#ucsc-VirtualBox:~/Desktop/Question$

You do not have javac, the java compiler installed. Follow the recommendation given - install one from the variations offered. I'd suggest openjdk-7-jdk.

You don't have a java compiler installed (javac). Use 'sudo apt-get install openjdk-7-jdk' to install it.

You don't have a JDK installed on your ubuntu system so the javac command to compile your program doesn't exist. Just run the command like it says to install something that has it. I would go with defualt-jdk since I assume that Ubuntu would know to download the Java8 packages in an update when they are switched to be the default while the openjdk ones will not.
sudo apt-get install default-jdk

javac : command not found

I have installed java in my CentOS release 5.5 machine using the command yum install java. But I am unable to compile a class using javac.
Do I need to install any other package?
I have tried to locate the javac executable but i am unable to locate it.
/usr/bin/java is linked as follows:
/usr/bin/java -> /etc/alternatives/java
/etc/alternatives/java -> /usr/lib/jvm/jre-1.6.0-openjdk.x86_64/bin/java
I have seen the following output by yum list installed |grep java:
java-1.6.0-openjdk.x86_64 1:1.6.0.0-1.16.b17.el5 installed
tzdata-java.x86_64 2011b-1.el5 installed

Worked for me with this command:
yum install java-devel

You installed the Java Runtime Environment (JRE) only, which does not provide javac. For javac, you have to install the OpenJDK Development Environment. You can install java-devel or java-11-devel, which both include javac.
By the way: you can find out which package provides javac with a yum search, e.g.
su -c 'yum provides javac'
on more recent releases of CentOS e.g. 6 the command changes to
su -c 'yum provides */javac'

Use the following sudo command:
sudo yum install java-1.6.0-openjdk-devel

I don't know exactly what yum install java will actually install. But to check for javac existence do:
> updatedb
> locate javac
preferably as root. If it's not there you've probably only installed the Java runtime (JRE) and not the Java Development Kit (JDK). You're best off getting this from the Oracle site: as the Linux repos may be slightly behind with latest versions and also they seem to only supply the open-jdk as opposed to the Oracle/Sun one, which I would prefer given the choice.

I use Fedora (currently 31)
Even with JDK's installed, I still need to specify JAVAC_HOME in the .bashrc, especially since I have 4 Java versions using sudo alternatives --configure java to switch between them.
To find java location of java selected in alternatives
readlink -f $(which java)
In my case:
/usr/java/jdk1.8.0_241-amd64/jre/bin/java
So I set following in .bashrc to:
export JAVA_HOME=/usr/java/jdk1.8.0_241-amd64/jre/bin/java
export JAVAC_HOME=/usr/java/jdk1.8.0_241-amd64/bin/javac
export PATH=$PATH:/usr/java/jdk1.8.0_241-amd64/jre/bin
export PATH=$PATH:/usr/java/jdk1.8.0_241-amd64/bin/
Now javac –version gives:
javac 1.8.0_241
This is useful for those who want to use Oracle's version. Just remember to change your .bashrc again if you make a change with java alternatives.

Is the javac executable in a directory that is part of your PATH?
I don't know the CentOS equivalent of the Windows path but if you cd to the java sdk directory and run ./javac does anything happen?

Install same version javac as your JRE
yum install java-devel

This worked for me:
sudo dnf install java-<version>-devel

You have installed the Java Runtime Environment(JRE) but it doesn't contain javac.
So on the terminal get access to the root user sudo -i and enter the password.
Type yum install java-devel, hence it will install packages of javac in fedora.

Linux Mint 19.3
I installed Java Oracle manually, like this:
$ sudo ln -s /usr/lib/jvm/java-1.8.0_211/bin/javac /usr/bin/javac

for java 8 use
sudo yum install java-1.8.0-openjdk-devel

Make sure you install JDK/JRE first.
follow these steps:
open terminal go to your root dictionary by typing
cd /
you will see Library folder
Now follow this path Library/Java/JVM/bin
Once you get into bin you can see the javac file
Now you need to get the path of this folder for that just write this command
pwd
get the path for your javac.

Java installation issues on Ubuntu

Trying to install Java (JDK 6) on my new Ubuntu system and getting some bizarro errors. This is my first time ever using any flavor of Linux and so I'm sure it's a user issue (permissions or otherwise).
I downloaded the BIN file directly off Oracle's site (Java SE 6u23 for 64-bit Linux). This defaulted to downloading to /home/myUserName/Downloads.
From there I moved the file to /opt/java, which was a directory I created, because (as a Linux novice) that made sense to be the directory where Java should go.
I then ran the following 2 commands, per instruction I found online for running BINs:
chmod +x jdk-6u23-linux-x64.bin
sudo ./jdk-6u23-linux-x64.bin
Now, in my /opt/java directory I see both the BIN file and the jdk1.6.0_23 directory that seems to be intact upon inspection.
But, when I open a new terminal and run java -version, I get:
The program 'java' can be found in the following packages:
- gcj-4.4-jre-headless
- gcj-4.5-jre-headless
- openjdk-6-jre-headless
Try: sudo apt-get install
What is going on here?!?
(1) Was I wrong to try and make /opt/java my Java directory?
(2) Did I run the wrong commands?
(3) Is Java 1.6.0_23 even installed on my machine?
(4) What are all those gcj-xxx-headless targets?!?!
Thanks for any input!

Was I wrong to try and make /opt/java my Java directory?
Not really. Many Java developers install multiple JDK installations and always use /opt/jdk1.6.0_23 or similar paths. The bin file you downloaded is not an installer, but merely an extractor. It does not install the java binaries into system folders like /bin.
I usually download the JDK and execute it from within my home folder and afterwards move it to /opt and performing an chown.
Did I run the wrong commands?
Not really. In case you wanted to install a separate JDK, you did it correctly. In case you wanted system integration, you would be better off to use the distribution-specific packages, such as the one installed via aptitude install sun-java6-jdk or alike.
The bin you downloaded is imho more flexible, since I can use it to install multiple verisons of Java on the same system. I know this is something you don't often do on Linux machines.
If you want to use the java binary on command line, you'd have to manually set up the PATH and JAVA_HOME environment variables. I think on Ubuntu that's /etc/environment or /etc/profile or something like that.
Is Java 1.6.0_23 even installed on my machine?
Not really. See above answers.
What are all those gcj-xxx-headless targets?!?
The GCJ is the Gnu Compiler for Java. Obviously, it includes a Java Development Kit and a Java Runtime Environment.

Why downloading a bin, when you can simply:
sudo apt-get install sun-java6-jdk
If there isn't any special reason why you'd want that specific version from the site, you should use apt-get because it will take care of all the stuff like PATH variable, etc.

Please follow below steps to install oracle java:
Download the latest Java SE SDK version.
http://www.oracle.com/technetwork/java/javase/downloads/index.html
Untar the Archive:
tar -xzvf jdk-8-linux-x64.tar.gz
mv jdk1.8.0 /opt
cd /opt/jdk1.8.0
This step registers the downloaded version of Java as an alternative, and switches it to be used as the default:
update-alternatives --install /usr/bin/java java /opt/jdk1.8.0/bin/java 1
update-alternatives --install /usr/bin/javac javac /opt/jdk1.8.0/bin/javac 1
update-alternatives --install /usr/lib/mozilla/plugins/libjavaplugin.so mozilla-javaplugin.so /opt/jdk1.8.0/jre/lib/amd64/libnpjp2.so 1
update-alternatives --set java /opt/jdk1.8.0/bin/java
update-alternatives --set javac /opt/jdk1.8.0/bin/javac
update-alternatives --set mozilla-javaplugin.so /opt/jdk1.8.0/jre/lib/amd64/libnpjp2.so
Test
To check the version of Java you are now running
java -version
Output
java version "1.8.0"
Java(TM) SE Runtime Environment (build 1.8.0-b132)
Java HotSpot(TM) 64-Bit Server VM (build 25.0-b70, mixed mode)
To check the browser plugin browse to http://www.java.com/ and click “Do I have Java?”
Ref: https://askubuntu.com/questions/437776/ubuntu-13-04-unable-to-install-jdk7

You simply have put the JDK binaries in a directory. Although by convention /opt/java or /opt/jdk is often used, these are not directories that are automatically recognized by the system.
You can however update your PATH environment variable to include the /opt/java/bin dir, or symlink (ln -s) /opt/java/bin/java in one of the directories on your system that are included in your path like /usr/bin/

The JDK you installed from Sun/Oracle is the original JDK. The "headless" JDK is the open source alternative.
When you run the JDK BIN file, it simply extracts the archive. When you entered the java -version command, it found the FOSS Java, not the Java you had extracted in /opt. As somebody else had mentioned, developers keep multiple versions of the JDK. If you wish to use the Oracle's Java, then you need link /usr/bin/java to /opt/jdk1.6.0_23/bin/java.
sudo ln -s /usr/bin/java /opt/jdk1.6.0_23/bin/java
For this to work, the existing java command should be first delinked from the "headless" JDK. (Do the following before the previous command.)
sudo mv /usr/bin/java /usr/bin/java_old
This assumes that there is a link or executable named java in /usr/bin. Use the which command to be sure.
which java

To add a new pathname to the existing PATH variable, you need to type this in Terminal:
PATH=`echo $path`:/your/new/path
export PATH
If you had lost your original PATH variable, you could restore by entering this:
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
export PATH

Try:
rm -rf /usr/bin/javac
rm -rf /usr/bin/jar
ln -s /home/jdk1.6.0_13/bin/javac /usr/bin/javac
ln -s /home/jdk1.6.0_13/bin/jar /usr/bin/jar
This way, your linux can find java && javac in /usr/bin

Can `apt-get install` be used for JDK?

I've been using a linux machine for less than two weeks, so I am extremely new to Linux.
I'd also like to install the Java Developers Kit. How should this be done? Is there an apt-get command, or should I just click on the download button at Sun's website?
I'm sure there is more than one way to do this, and it probably doesn't matter much, but I was impressed with how smoothly apt-get install worked when installing PHP and MySQL, so if there is a right way to do this, I'd like to know.
I'm using Ubuntu version 9.04

Yes, definitely it's the suggested way to install JDK on your Linux system (if available).
On Ubuntu:
sudo apt-get install sun-java6-jdk

The Oracle JDK is no longer included in the Ubuntu repos. According to https://stackoverflow.com/a/15543636/192221 , the following ppa can be used:
echo "deb http://ppa.launchpad.net/webupd8team/java/ubuntu precise main" | tee -a /etc/apt/sources.list
echo "deb-src http://ppa.launchpad.net/webupd8team/java/ubuntu precise main" | tee -a /etc/apt/sources.list
apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys EEA14886
apt-get update
apt-get install oracle-java7-installer
If you have OpenJDK installed already, you might need to use
update-alternatives --config java
to use the Oracle Java by default.

If you for some reason need to install the sun packages you can use the make-jpkg command to create a deb file and still have the files managed by apt/dpkg.
To do this:
sudo apt-get install java-package
fakeroot make-jpkg jre-1_5_0_06-linux-i586.bin
you will then have a .dpg file that you can install using for example gdebi
gdebi-gtk jre.deb
Also note that you can have multiple JDKs installed and switch between them using update-alternatives:
update-alternatives --config java
update-alternatives --config javac
and so on for other java related binaries, have a look in /etc/alternatives to find out which are available.

In Ubuntu 9.10 Karmic Koala apt-get and the Synaptic Software Manager both install version 6.15.1 of Sun Java and the JDK, which are now out of date, and an old version of Netbeans,, so don't use "sudo apt-get install" for these.
Go to the Sun Java download page
http://www.java.com/en/download/manual.jsp
Select the non-RPM 32-bit or 64-bit self extracting file, download it and check the file size of the downloaded file. Doesn't matter where you download it.
Click on the link to installation instructions for the corresponding file.
An easier way to set executable permission is to right click on the file in the file browser (Nautilus) and click Properties, then on the Permissions tab, click the Execute checkbox.
To test, open a new terminal and type:
java -version
You should see Java version "1.6.0_18" etc.
If you don't, you probably need to add some lines, adjusted to suit your installation directories, to .bashrc and .bash_profile which are both hidden files in your home directory.
gedit .bashrc
Add the following:
export JAVA_HOME=/opt/java/64/jre1.6.0_18
export PATH=$PATH:$JAVA_HOME/bin
Then edit your .bash_profile file and insert the same lines at the end:
gedit .bash_profile
Open a new terminal window and test as above.
If all went well, in the Applications menu > System Tools, you should now have the Sun Java Control Panel.
You can repeat a similar installation procedure for the JDK and Netbeans where you mark the downloaded .bin file as executable and then execute it from a terminal window in the directory you want to install into, such as /usr/local.
After installing the JDK, add to your .bashrc and .bash_profile files a line similar to this:
export PATH=$PATH:/usr/local/jdk1.6.0_18/bin
Netbeans 6.8 seems to be able to set itself up ok without any editing and adds itself to the Applications Programming menu.

My Ubuntu box has sun-java5-jdk and sun-java6-jdk available.

I am personally a linux mint person. However, I couldn't find this in my respitory:
sudo apt-get install sun-java6-jdk
After poking around for a bit, I was able to get this to work.
sudo apt-get install openjdk-6-jdk
Cheers.

I'm not sure Ubuntu 9.04. Is it openJDK?
But in Ubuntu 9.10 It is openJDK.
So It have many problem.
You can do like this to remove and install sun java jdk
sudo apt-get remove openJDK*
sudo apt-get install sun-java6*