/**
 * Executes the given command at some time in the future.  The command
 * may execute in a new thread, in a pooled thread, or in the calling
 * thread, at the discretion of the {@code Executor} implementation.
 *
 * @param command the runnable task
 * @throws RejectedExecutionException if this task cannot be
 * accepted for execution
 * @throws NullPointerException if command is null
 */
void execute(Runnable command); }