Returns the common pool instance. This pool is statically
constructed; its run state is unaffected by attempts to {@link
#shutdown} or {@link #shutdownNow}. However this pool and any
ongoing processing are automatically terminated upon program
{@link System#exit}. Any program that relies on asynchronous
task processing to complete before program termination should
invoke {@code commonPool().}{@link #awaitQuiescence awaitQuiescence},
before exit.
Returns the common pool instance. This pool is statically constructed; its run state is unaffected by attempts to {@link #shutdown} or {@link #shutdownNow}. However this pool and any ongoing processing are automatically terminated upon program {@link System#exit}. Any program that relies on asynchronous task processing to complete before program termination should invoke {@code commonPool().}{@link #awaitQuiescence awaitQuiescence}, before exit.
@return the common pool instance