'tools.jar' seems to be not in Phpstorm classpath.

Trying to lunch PHPstorm I got this message:

'tools.jar' seems to be not  in Phpstorm classpath. 

Please ensure JAVA_HOME points to JDK rather than JRE.

My system : Lubuntu 16.10 

$ java -version
openjdk version "9-Ubuntu"
OpenJDK Runtime Environment (build 9-Ubuntu+0-9b134-2ubuntu1)
OpenJDK Client VM (build 9-Ubuntu+0-9b134-2ubuntu1, mixed mode)

When I checked /usr/lib/jvm/java-9-openjdk-i386/docs/JAVA_HOME file

JAVA_HOME

1. Legacy use of JAVA_HOME

As of the latest versions of java-common there really should
be no need for JAVA_HOME as Java(TM) should be completely
integrated with your Debian GNU/Linux system.

2. Selecting OpenJDK 7 as the default Java(TM) implementation

Please see README.alternatives for instructions on how
to make OpenJDK 7 executables and man pages the default on your system.

So whats the solution now? I'm confused..