Undefined entities in Understand projects can lead to inaccuracies in the parse and other oddities. One of the easiest ways to enhance project accuracy and define a lot of built in base objects for Java is by adding a couple of Classpaths for the JDK your code targets. 

Specifically, the files “java.base.jmod” and “src.zip” have many definitions in them that can resolve uncertainties in the code. The easiest way to add these to your project is in Project->Configure Project->Java->Class Paths. Hit the “New Jar” button and navigate to these files, one at a time.