Q:

java -version doesn't display the value of JAVA_HOME

I've installed jdk 7 and set up the "JAVA_HOME" to this version. Then, I've installed jdk 6 and I've updated the "JAVA_HOME" to point to jdk 6. After closing and reopening the system, when typing "java -version", I got always :
java version "1.7.0_40"
Java(TM) SE Runtime Environment (build 1.7.0_40-b43)
Java HotSpot(TM) Client VM (build 24.0-b56, mixed mode, sharing)

However, when typing 
echo %JAVA_HOME%

I got : 
C:\Program Files\Java\jdk1.6.0_45

I didn't understand why java -version don't display the value of "JAVA_HOME"

A:

Java 7 puts a java.exe in c:\windows\system32. You could try to delete these exe's, but I'm not sure Windows will allow it, or restore it after a reboot.
If you want to override it, you must put %JAVA_HOME%\bin as first entry in your PATH, before c:\windows\system32.

