System classes while enabling Assertions, what are they? [duplicate]

Question

This question already has answers here:

Which are Java's system classes? (2 answers)

Closed 6 years ago.

What do they mean with System classes in the following statement taken from the official documentation?

To enable assertions at various granularities, use the -enableassertions, or -ea, switch. To disable assertions at various granularities, use the -disableassertions, or -da, switch. You specify the granularity with the arguments that you provide to the switch:

• no arguments
  Enables or disables assertions in all classes except system classes.
• ...

(emphasis mine).

Answer 1

"System classes" are those loaded by the boot class loader. For all intents and purposes, this means the classes documented in the standard Java APIs.