The following problems are reported:

• Use of assert>, enum or _ as an identifier
• Use of the var, yield, or record restricted identifier as a type name
• Unqualified calls to the yield method
• Modifiers on the requires java.base statement inside of module-info.java

Example:

  // Since Java 14, this class will stop compiling, as 'yield' becomes a restricted identifier.
  public class yield {} 

Fixing these issues timely may simplify migration to future Java versions.