unable to add platform

JAVA Home is set and JDK installed. But:

C:\wamp\www\projects\mfeedback>cordova requirements

Requirements check results for android:
Java JDK: not installed
Failed to run "javac -version", make sure that you have a JDK installed.
You can get it from: http://www.oracle.com/technetwork/java/javase/downloads.
Your JAVA_HOME is invalid: C:\Program Files\Java\jdk1.8.0_31

Android SDK: installed true
Android target: installed android-21,android-23,android-24,android-25,Google Inc.:Google APIs:21
Gradle: installed
Error: Some of requirements check failed

C:\wamp\www\projects\mfeedback>javac -version
Fehler: Hauptklasse com.sun.tools.javac.Main konnte nicht gefunden oder geladen werden