B.4. RuntimeException

The RuntimeException is not thrown directly by any of the methods in the thread classes; it is simply a base class that specifies a special group of exceptions. Runtime exceptions are considered so basic that it would be too tedious to check for every possible runtime exception that could be thrown (another reason is that these exceptions are generally bugs in the program). Unlike other exceptions, the compiler does not require that you handle a RuntimeException.

All of the following exceptions are runtime exceptions.