Checked and Unchecked Exceptions

Except for RuntimeException, Error, and their subclasses, all exceptions are called checked exceptions. The compiler ensures that if a method can throw a checked exception, directly or indirectly, then the method must explicitly deal with it. The method must either catch the exception and take the appropriate action, or pass the exception on to its caller.
Exceptions defined by Error and RuntimeException classes and their subclasses are known as unchecked exceptions, meaning that a method is not obliged to deal with these kinds of exceptions. They are either irrecoverable (exemplified by the Error class) and the program should not attempt to deal with them, or they are programming errors (examplified by the RuntimeException class) and should be dealt with as such and not as exceptions.
Any method that can cause a checked exception to be thrown, either directly by using the throw statement or indirectly by invoking other methods that can throw such an exception, must deal with the exception in one of three ways. It can

• use a try block and catch the exception in a handler and deal with it
• use a try block and catch the exception in a handler, but throw another exception that is either unchecked or declared in its throws clause
• explicitly allow propagation of the exception to its caller by declaring it in the throws clause of its method prototype