Unsafe1 article

As we know, sun.misc.Unsafe APIs are not recommended to use outside the JDK, with a slight mistake it may result in a JVM crash. In some cases, code may not be portable across different platforms and many other problems that may occur.

Classes that cannot be used directly by the bytecode of other classes are hidden classes. Hidden classes allow frameworks/JVM languages to define classes as non-discoverable implementation details, so that they cannot be linked against by other classes.