You may be confusing Java language specification with the Java Platform programming API. Language spec has very limited set of packages generally in java.lang

You may be confusing Java language specification with the Java Platform programming API. Language spec has very limited set of packages generally in java.lang. https://docs.oracle.com/javase/specs/jls/se14/html/index.html https://docs.oracle.com/javase/specs/jls/se14/html/index.htm... Platform API is here https://docs.oracle.com/javase/10/docs/api/overview-summary.html https://docs.oracle.com/javase/10/docs/api/overview-summary....