Scheduledexecutorservice timed tasks, threads

After Java5, the concurrent Threads section adds a lot of new things, a new start, dispatch, and management thread of a lot of API, at this time through executor to start the thread than Thread.Start () better, easier to control thread startup, destruction, etc., can also use the function of the thread pool.

I. Creating a Task

is actually implementing the Runnable interface to implement the Run method.

Two. Perform Tasks

The task is performed through the Java.util.concurrent.ExecutorService interface object, which is created through a static method of the tool class java.util.concurrent.Executors.

Executors factory and utility methods for the Executor, Executorservice, Scheduledexecutorservice, Threadfactory, and callable classes defined in this package.

1. Create thread pool (for Scheduledexecutorservice)

private static Scheduledexecutorservice Singlescheduler = Executors.newscheduledthreadpool (4);

2. Adding tasks to the thread pool

When a task is added to the thread pool, the thread pooling assigns each task a task to run. The execution time can be timed and can be temporary.

(1) Perform temporary tasks

Scheduledexecutorservice has two better ways to perform a temporary task execute (), submit ()

Three differences:

A. Different parameters

Execute () has only one method to receive the Runnable class,

Submit () has three overloaded methods, receiving the Runnable class, callable class, and runnable, respectively, T (the value to perform a successful return)

B. return value

Execute () has no return value, and submit () has an identity that returns whether a future<> is successful after execution. If a task executes, you need to know if the execution succeeds, and if it fails, what the cause is.

C.submit Convenient exception handling

(2) Perform timed tasks Scheduleatfixedrate,schedulewithfixeddelay

A.scheduleatfixedrate

Specific parameter description

Public scheduledfuture<?> scheduleatfixedrate (Runnable command, long initialdelay,Long Period, timeunit unit);

command execution of the thread; InitialDelay initialization delay; period; two starts execution minimum time interval; Unit timing units

B.schedulewithfixeddelay

Specific parameter description

Public scheduledfuture<?> schedulewithfixeddelay (Runnable command, long initialdelay,long delay, Timeunit unit);

command execution thread; initialdelay initialization delay; interval (interval execution delay) at the end of the previous execution to the start of the next execution; Unit time units

Third, close the object

　　Shutdown ();

Iv. examples

　1. Simple Runnable class

Excute () and submit () the execution of a single parameter is relatively simple and not listed.

　　

 Package test;  Public class Implements runnable{    public  Threaddemo () {            }    @Override    public  void  Run () {        System.out.println ("simple execution!") );    }}

2. Execution of temporary tasks

　　

 Packagetest;Importjava.util.concurrent.ExecutionException;Importjava.util.concurrent.Executors;Importjava.util.concurrent.Future;ImportJava.util.concurrent.ScheduledExecutorService; Public classTestthread {Private StaticScheduledexecutorservice Singlescheduler = Executors.newscheduledthreadpool (4);  Public Static voidMain (string[] args) { future<String> F =singlescheduler.submit (NewThreaddemo (), "Success!"); Try{System.out.println (F.get ()); } Catch(interruptedexception e) {e.printstacktrace (); }  Catch(executionexception e) {e.printstacktrace (); }            }} 

return results

Simple Execution! Success !

3. Execution of timed tasks

Schedulewithfixeddelay differs from this method only with some differences in parameters.

 Packagetest;Importjava.util.concurrent.Executors;ImportJava.util.concurrent.ScheduledExecutorService;ImportJava.util.concurrent.TimeUnit; Public classTestthread {Private StaticScheduledexecutorservice Singlescheduler = Executors.newscheduledthreadpool (4);  Public Static voidMain (string[] args) {singlescheduler.scheduleatfixedrate (NewThreaddemo (), 1, 1, Timeunit.seconds); }} 

return results

　　

Simple Execution! Simple Execution ! Simple Execution ! Simple Execution ! Simple Execution !

Scheduledexecutorservice timed tasks, threads