Package java. lang ClassDescriptionCompilerThe Compiler class is provided to support Java-to-native-code compilers and related services.DoubleThe Double class wraps a value of the primitive type double in an object.Enum<E extends Enum<E>>This is the common base class of all Java language enumeration types.Package java.lang – Oracle Help Center docs.oracle.com › javase › docs › api › java › lang › package-summary