Executor interface in java

I. Structure

Located in the java. util. concurrent package. Declared as: public interfaceExecutor

All known sub-interfaces: ExecutorService, ScheduledExecutorService all known implementation classes: AbstractExecutorService, ScheduledThreadPoolExecutor, ThreadPoolExecutor II. Overview:

Execute submittedRunnableTask object. This interface provides a way to separate job submission from how each job runs (including details about thread usage and scheduling. GenerallyExecutorInstead of explicitly creating a thread. For example, you may use the following method instead of calling each task in a group of tasks.New Thread (new (RunnableTask (). start ():

 Executor executor = anExecutor; executor.execute(new RunnableTask1()); executor.execute(new RunnableTask2()); ...

However,ExecutorThe interface does not strictly require that the execution be asynchronous. In the simplest case, the execution program can immediately run the submitted task in the caller's thread:

 class DirectExecutor implements Executor {     public void execute(Runnable r) {         r.run();     } }

More often, tasks are executed in a thread that is not the caller's thread. The following execution program generates a new thread for each task.

 class ThreadPerTaskExecutor implements Executor {     public void execute(Runnable r) {         new Thread(r).start();     } }

ManyExecutorThe implementation imposes some restrictions on the way and time of scheduling tasks. The following execution programs keep the task submission in sequence with the second execution program, which shows a composite execution program.

 class SerialExecutor implements Executor {     final Queue
 
   tasks = new ArrayDeque
  
   ();     final Executor executor;     Runnable active;     SerialExecutor(Executor executor) {         this.executor = executor;     }     public synchronized void execute(final Runnable r) {         tasks.offer(new Runnable() {             public void run() {                 try {                     r.run();                 } finally {                     scheduleNext();                 }             }         });         if (active == null) {             scheduleNext();         }     }     protected synchronized void scheduleNext() {         if ((active = tasks.poll()) != null) {             executor.execute(active);         }     } }
  
 

TheExecutorImplementedExecutorService, Which is a more widely used interface.ThreadPoolExecutorClass provides an extensible thread pool implementation.ExecutorsClass provides convenient factory methods for these executors.

Memory consistency effect: the thread willRunnableObject submittedExecutorPrevious operationsHappen-beforeThe execution starts (possibly in another thread ).

Iii. Detailed method:

VoidExecute(Runnable command)

Execute a given command at a certain time in the future. This command may be executed in a new thread, a thread in the pool, or a calling thread.ExecutorImplementation decisions.

Parameters:command-Runable tasks

Throw:RejectedExecutionException-If the task cannot be executed.

NullPointerException-If the command is null