| A task that returns a result and may throw an exception.
Implementors define a single method with no arguments called
call.
The Callable interface is similar to {@link
java.lang.Runnable}, in that both are designed for classes whose
instances are potentially executed by another thread. A
Runnable, however, does not return a result and cannot
throw a checked exception.
The {@link Executors} class contains utility methods to
convert from other common forms to Callable classes. | 