Properly installing java 8 along with java 7

Question

I've JDK 1.7 installed on my windows 7 machine and after installing JDK 1.8 u20 I'm having following error:

C:\>java -version
Error: Registry key 'Software\JavaSoft\Java Runtime Environment'\CurrentVersion'
has value '1.8', but '1.7' is required.
Error: could not find java.dll
Error: Could not find Java SE Runtime Environment.

My PATH variable points to the older version (i.e. 1.7).

What is wrong here and how I could use java 8 along with java 7?

Answer 1

The problem is that Java 8 installs a lot of stuff that you don't really need:

• \windows\system32 contains Java 8 java.exe, javaw.exe and javaws.exe. Your path probably has system32 near the beginning, so these tend to be run by default.

• The system path variable starts with C:\programdata\Oracle\Java\javapath. This folder contains java.exe, javaw.exe and javaws.exe as symlinks to the JRE 8 executables.

I've deleted the system32 files and removed C:\programdata\Oracle\Java\javapath from the system path. This seems to cure the problem. I can now switch versions by pointing JAVA_HOME and PATH to the appropriate folders.

Oracle, it seems, are determined to make it hard to run multiple versions. This is understandable with the JRE, but it's crazy with JDKs, as developers almost always need multiple versions of Java.

EDIT: I find this batch script is useful for switching JDKs. Usage: jdk.bat 6|7|8. You might have to edit the installation location for Java.

@echo off
if "%1"=="" goto report
set _version=%1
shift
if "%1"=="DBG" shift & echo on
set _command=%1 %2 %3 %4 %5

set _jdkdir=
set _jdkver=
for /D %%f in ("C:\Program Files\java\"jdk1.%_version%.*) do call :found "%%f"
if "%_jdkdir%"=="" goto notfound

set java_home=C:\Program Files\java\%_jdkdir%
call :javapath
path %new_path%
goto :report

:javapath
    setlocal enabledelayedexpansion
    set _jdirs=
    for /D %%j in ("C:\Program Files\java\*") do set _jdirs=!_jdirs!#%%~fj\bin
    set _jdirs=%_jdirs%#

    set _javabin=%java_home%\bin
    set _fpath="%PATH:;=" "%"
    call :checkpath %_fpath%
    endlocal & set new_path=%_javabin%
goto :eof

:checkpath
    if _%1==_ goto :eof
    echo %_jdirs% | find /i "#%~1#" 1>nul 2>&1
    set _err=%errorlevel%
    if not %_err%==0 set _javabin=%_javabin%;%~1
    if %_err%==0 echo Removed %~1 from path
    shift
    goto :checkpath

:report
javac -version
%_command%
goto :eof

:notfound
echo No JDK matching [C:\Program Files\java\jdk1.%_version%.*] found.
goto :eof

:found
set _jdkdir=%~n1%~x1
for /F "tokens=2,3 delims=." %%a in ("%_jdkdir%") do set _jdkver=1.%%a.%%b
goto :eof