Your next step is to compile your application using JDK 9's javac. This is important, even if your app works fine on JDK 9. You might not receive compiler errors, but watch for warnings too. Here are the most common reasons your applications might not compile with JDK 9, assuming they compiled fine prior to Java 9.
First, as indicated earlier in this chapter, most of the JDK 9 internal APIs are not accessible by default. Your indication will be an IllegalAccessErrors error at runtime or compile time. You will need to update your code so that you are using accessible APIs.
A second reason your pre-Java 9 applications might not compile with JDK 9 is if you use the underscore character as a single character identifier. ...
