A few customers have asked about using Java 9 with MyEclipse. There are several aspects to this.
Running the installers with a Java 9 VM
This should not be a problem. However, some eclipse installers don’t appear to work and so they must be run from the command line specifying the vm to use with the -vm option with a path to the appropriate java executable.
Running MyEclipse with a Java 9 VM
Though there is no reason to run MyEclipse with Java 9 as a Java 8 JDK is included with MyEclipse, you can specify the Java 9 VM in the myeclipse.ini file (eclipse.ini file on a Mac) but you then need to add --add-modules=ALL-SYSTEM to the -vmargs section.
Defining a Java 9 JRE and using new Java 9 features
This is not possible with MyEclipse 2017 as Java 9 support is only to be added to eclipse Oxygen (4.7) and later, but MyEclipse 2017 is based on eclipse Neon (4.6). Support for Java 9 will be added to MyEclipse 2018, which is based on eclipse Oxygen, and is scheduled for a 4Q2017 release.
Please raise any further questions about this in the appropriate support forum.