There is not a "proper" (as in supported or recommended by JDK providers) way to install or use Java on WSL. I could not find any official recommendations.

However, it is possible to either install and use Oracle JDK for Windows installation from WSL, or install OpenJDK Java into your WSL world from the Ubuntu package manager.

I was just wondering if I need to install all the development tools and binaries again on Linux won't it take a lot of space & hog a lot of CPU/Ram resources ?

See above. But note that you are only going to "hog CPU/RAM" if you are running both kinds of JVM at the same time.

References:

• Installing Oracle JDK on Windows subsystem for Linux
• Java JDK 11 install script for Windows Subsystem for Linux (WSL)
• Windows Subsystem for Linux Java Setup ... using the Ubuntu package system.

^{(There are many more articles on this topic if the above don't address your concerns.)}

We can use that Windows JDK inside the wsl2. we should add this to /etc/environment

JAVA_HOME=/mnt/c/Program Files/Java/jdk-11.0.8/bin/

by adding this bin folder we may run regular commands but append with .exe format eg: javac.exe hello.java java.exe hello.java

if you don't like that way then add alias like below:

alias java='java.exe'
alias javac='javac.exe'

I think we can use any of the windows programs like this :)

Run the following commands as a user with sudo privileges or root to update the packages index and install the OpenJDK 11 JDK package:

$ sudo apt update
$ sudo apt install openjdk-11-jdk

Once the installation is complete, you can verify it by checking the Java version:

$ java -version

The output should look something like this:

openjdk version "11.0.7" 2020-04-14
OpenJDK Runtime Environment (build 11.0.7+10-post-Ubuntu-3ubuntu1)
OpenJDK 64-Bit Server VM (build 11.0.7+10-post-Ubuntu-3ubuntu1, mixed mode, sharing)

Set JAVA_HOME Environment Variable: OpenJDK 11 is located at /usr/lib/jvm/java-11-openjdk-amd64/bin/java

Once you found the path of your preferred Java installation, open the /etc/environment file:

$ sudo nano /etc/environment

Assuming you want to set JAVA_HOME to point to OpenJDK 11, add the following line, at the end of the file:

JAVA_HOME="/usr/lib/jvm/java-11-openjdk-amd64"

For changes to take effect on your current shell you can either log out and log in or run the following source command:

$ source /etc/environment

Verify that the JAVA_HOME environment variable was correctly set:

$ echo $JAVA_HOME

You should see the path to the Java installation:

/usr/lib/jvm/java-11-openjdk-amd64

for reference you can follow this link below How to Install Java on Ubuntu 20.04