Historically (up to JDK 1.8), documentation for the `java.awt.Toolkit` class referred to the "awt.toolkit" system property, which was set to the name of the platform implementation subclass. The documentation of this property was removed in JDK 9 because (1) it was an internal detail not intended to be a supported interface and (2) encapsulation by the module system meant that the class could not be directly manipulated. However, the system property was not removed until now. Applications that previously read this property can still, if necessary, obtain it by instantiating the AWT Toolkit and querying the class name via that instance.