$ which java

$ which java
/usr/bin/java
$ ls -l /usr/bin/java
lrwxr-xr-x  1 root  wheel  74 Nov  7 07:59 /usr/bin/java -> /System/Library/Frameworks/JavaVM.framework/Versions/Current/Commands/java

c:> for %i in (java.exe) do @echo.   %~$PATH:i

C:> for %i in (javac.exe) do @echo.   %~$PATH:i

@echo off

setlocal

::- Get the Java Version
set KEY="HKLMSOFTWAREJavaSoftJava Runtime Environment"
set VALUE=CurrentVersion
reg query %KEY% /v %VALUE% 2>nul || (
    echo JRE not installed
    exit /b 1
)
set JRE_VERSION=
for /f "tokens=2,*" %%a in ('reg query %KEY% /v %VALUE% ^| findstr %VALUE%') do (
    set JRE_VERSION=%%b
)

echo JRE VERSION: %JRE_VERSION%

::- Get the JavaHome
set KEY="HKLMSOFTWAREJavaSoftJava Runtime Environment%JRE_VERSION%"
set VALUE=JavaHome
reg query %KEY% /v %VALUE% 2>nul || (
    echo JavaHome not installed
    exit /b 1
)

set JAVAHOME=
for /f "tokens=2,*" %%a in ('reg query %KEY% /v %VALUE% ^| findstr %VALUE%') do (
    set JAVAHOME=%%b
)

echo JavaHome: %JAVAHOME%

endlocal

try{Thread.sleep(60000);}catch(Exception e) {}

// File: Main.java
public class Main {

    public static void main(String[] args) {
       System.out.println(System.getProperty("java.home"));
    }

}


$ javac Main.java
$ java Main

set java_home

C:>dir /b /s java.exe

$ set | grep "JAVA_HOME"

which java

echo %PATH%

set "JAVA_HOME"

#!/bin/bash

if [[ $(which ${JAVA_HOME}/bin/java) ]]; then
    exe="${JAVA_HOME}/bin/java"
elif [[ $(which java) ]]; then
    exe="java"
else
    echo "Java environment is not detected."
    exit 1
fi

${exe} -version

@echo off
if "%JAVA_HOME%" == "" goto nojavahome

echo Using JAVA_HOME            :   %JAVA_HOME%

"%JAVA_HOME%/bin/java.exe" -version
goto exit

:nojavahome
echo The JAVA_HOME environment variable is not defined correctly
echo This environment variable is needed to run this program.
goto exit

:exit

$p='HKLM:SOFTWAREJavaSoftJava Development Kit'; $v=(gp $p).CurrentVersion; (gp $p/$v).JavaHome