| Interface | Description | 
|---|---|
| Callable<V> | 
 A task that returns a result and may throw an exception. 
 | 
| Delayed | 
 A mix-in style interface for marking objects that should be acted upon after a given delay. 
 | 
| Executor | 
 An object that executes submitted  
Runnable tasks. | 
| ExecutorService | |
| Future<V> | 
 A Future represents the result of an asynchronous computation. 
 | 
| ScheduledExecutorService | 
 An  
ExecutorService that can schedule commands to run after a given delay, or to execute periodically. | 
| ScheduledFuture<V> | 
 A delayed result-bearing action that can be cancelled. 
 | 
| ThreadFactory | 
 An object that creates new threads on demand. 
 | 
| Enum | Description | 
|---|---|
| TimeUnit | 
 A TimeUnit represents time durations at a given unit of granularity and provides utility methods to convert
 across units, and to perform timing and delay operations in these units. 
 | 
| Exception | Description | 
|---|---|
| CancellationException | 
 Exception indicating that the result of a value-producing task, cannot be retrieved because the task was cancelled. 
 | 
| ExecutionException | 
 Exception thrown when attempting to retrieve the result of a task that aborted by throwing an exception. 
 | 
| RejectedExecutionException | 
 Exception thrown by an  
Executor when a task cannot be accepted for execution. | 
| TimeoutException | 
 Exception thrown when a blocking operation times out. 
 |