Executor executor = Executors.newFixedThreadPool(10); Runnable task = new Runnable() {     @Override    public void run() {         System.out.println("task over");     } }; executor.execute(task);   executor = Executors.newScheduledThreadPool(10); ScheduledExecutorService scheduler = (ScheduledExecutorService) executor; scheduler.scheduleAtFixedRate(task, 10, 10, TimeUnit.SECONDS);
二、ExecutorService与生命周期
ExecutorService扩展了Executor并添加了一些生命周期管理的方法。一个Executor的生命周期有三种状态，运行 ，关闭 ，终止 。Executor创建时处于运行状态。当调用ExecutorService.shutdown()后，处于关闭状态，isShutdown()方法返回true。这时，不应该再想Executor中添加任务，所有已添加的任务执行完毕后，Executor处于终止状态，isTerminated()返回true。
如果Executor处于关闭状态，往Executor提交任务会抛出unchecked exception RejectedExecutionException。
[java] view plain copy print?ExecutorService executorService = (ExecutorService) executor;   while (!executorService.isShutdown()) {       try {           executorService.execute(task);       } catch (RejectedExecutionException ignored) {                   }   }   executorService.shutdown();  
ExecutorService executorService = (ExecutorService) executor; while (!executorService.isShutdown()) {     try {         executorService.execute(task);     } catch (RejectedExecutionException ignored) {               } } executorService.shutdown();
三、使用Callable，Future返回结果
Future<V>代表一个异步执行的操作，通过get()方法可以获得操作的结果，如果异步操作还没有完成，则，get()会使当前线程阻塞。FutureTask<V>实现了Future<V>和Runable<V>。Callable代表一个有返回值得操作。
[java] view plain copy print?Callable<Integer> func = new Callable<Integer>(){           public Integer call() throws Exception {               System.out.println("inside callable");               Thread.sleep(1000);               return new Integer(8);           }              };             FutureTask<Integer> futureTask  = new FutureTask<Integer>(func);       Thread newThread = new Thread(futureTask);       newThread.start();               try {           System.out.println("blocking here");           Integer result = futureTask.get();           System.out.println(result);       } catch (InterruptedException ignored) {       } catch (ExecutionException ignored) {   }  
Callable<Integer> func = new Callable<Integer>(){ 	    public Integer call() throws Exception { 	        System.out.println("inside callable"); 	        Thread.sleep(1000); 	        return new Integer(8); 	    }        	};       	FutureTask<Integer> futureTask  = new FutureTask<Integer>(func); 	Thread newThread = new Thread(futureTask); 	newThread.start(); 	  	try { 	    System.out.println("blocking here"); 	    Integer result = futureTask.get(); 	    System.out.println(result); 	} catch (InterruptedException ignored) { 	} catch (ExecutionException ignored) { }
ExecutoreService提供了submit()方法，传递一个Callable，或Runnable，返回Future。如果Executor后台线程池还没有完成Callable的计算，这调用返回Future对象的get()方法，会阻塞直到计算完成。
例子：并行计算数组的和。
[java] view plain copy print?package executorservice;           import java.util.ArrayList;   import java.util.List;   import java.util.concurrent.Callable;   import java.util.concurrent.ExecutionException;   import java.util.concurrent.ExecutorService;   import java.util.concurrent.Executors;   import java.util.concurrent.Future;   import java.util.concurrent.FutureTask;       public class ConcurrentCalculator {           private ExecutorService exec;       private int cpuCoreNumber;       private List<Future<Long>> tasks = new ArrayList<Future<Long>>();           // 内部类       class SumCalculator implements Callable<Long> {           private int[] numbers;           private int start;           private int end;               public SumCalculator(final int[] numbers, int start, int end) {               this.numbers = numbers;               this.start = start;               this.end = end;           }               public Long call() throws Exception {               Long sum = 0l;               for (int i = start; i < end; i++) {                   sum += numbers[i];               }               return sum;           }       }           public ConcurrentCalculator() {           cpuCoreNumber = Runtime.getRuntime().availableProcessors();           exec = Executors.newFixedThreadPool(cpuCoreNumber);       }           public Long sum(final int[] numbers) {           // 根据CPU核心个数拆分任务，创建FutureTask并提交到Executor           for (int i = 0; i < cpuCoreNumber; i++) {               int increment = numbers.length / cpuCoreNumber + 1;               int start = increment * i;               int end = increment * i + increment;               if (end > numbers.length)                   end = numbers.length;               SumCalculator subCalc = new SumCalculator(numbers, start, end);               FutureTask<Long> task = new FutureTask<Long>(subCalc);               tasks.add(task);               if (!exec.isShutdown()) {                   exec.submit(task);               }           }           return getResult();       }           /**       * 迭代每个只任务，获得部分和，相加返回       *        * @return       */      public Long getResult() {           Long result = 0l;           for (Future<Long> task : tasks) {               try {                   // 如果计算未完成则阻塞                   Long subSum = task.get();                   result += subSum;               } catch (InterruptedException e) {                   e.printStackTrace();               } catch (ExecutionException e) {                   e.printStackTrace();               }           }           return result;       }           public void close() {           exec.shutdown();       }   }  int[] numbers = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 10, 11 };   ConcurrentCalculator calc = new ConcurrentCalculator();   Long sum = calc.sum(numbers);   System.out.println(sum);   calc.close();  
package executorservice; 	  import java.util.ArrayList; import java.util.List; import java.util.concurrent.Callable; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Future; import java.util.concurrent.FutureTask;   public class ConcurrentCalculator {       private ExecutorService exec;     private int cpuCoreNumber;     private List<Future<Long>> tasks = new ArrayList<Future<Long>>();       // 内部类     class SumCalculator implements Callable<Long> {         private int[] numbers;         private int start;         private int end;           public SumCalculator(final int[] numbers, int start, int end) {             this.numbers = numbers;             this.start = start;             this.end = end;         }           public Long call() throws Exception {             Long sum = 0l;             for (int i = start; i < end; i++) {                 sum += numbers[i];             }             return sum;         }     }       public ConcurrentCalculator() {         cpuCoreNumber = Runtime.getRuntime().availableProcessors();         exec = Executors.newFixedThreadPool(cpuCoreNumber);     }       public Long sum(final int[] numbers) {         // 根据CPU核心个数拆分任务，创建FutureTask并提交到Executor         for (int i = 0; i < cpuCoreNumber; i++) {             int increment = numbers.length / cpuCoreNumber + 1;             int start = increment * i;             int end = increment * i + increment;             if (end > numbers.length)                 end = numbers.length;             SumCalculator subCalc = new SumCalculator(numbers, start, end);             FutureTask<Long> task = new FutureTask<Long>(subCalc);             tasks.add(task);             if (!exec.isShutdown()) {                 exec.submit(task);             }         }         return getResult();     }       /**      * 迭代每个只任务，获得部分和，相加返回      *       * @return      */    public Long getResult() {         Long result = 0l;         for (Future<Long> task : tasks) {             try {                 // 如果计算未完成则阻塞                 Long subSum = task.get();                 result += subSum;             } catch (InterruptedException e) {                 e.printStackTrace();             } catch (ExecutionException e) {                 e.printStackTrace();             }         }         return result;     }       public void close() {         exec.shutdown();     } }int[] numbers = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 10, 11 }; ConcurrentCalculator calc = new ConcurrentCalculator(); Long sum = calc.sum(numbers); System.out.println(sum); calc.close();
四、CompletionService
在刚在的例子中，getResult()方法的实现过程中，迭代了FutureTask的数组，如果任务还没有完成则当前线程会阻塞，如果我们希望任意字任务完成后就把其结果加到result中，而不用依次等待每个任务完成，可以使CompletionService。生产者submit()执行的任务。使用者take()已完成的任务，并按照完成这些任务的顺序处理它们的结果 。也就是调用CompletionService的take方法是，会返回按完成顺序放回任务的结果，CompletionService内部维护了一个阻塞队列BlockingQueue，如果没有任务完成，take()方法也会阻塞。修改刚才的例子使用CompletionService：
[java] view plain copy print?public class ConcurrentCalculator2 {               private ExecutorService exec;       private CompletionService<Long> completionService;               private int cpuCoreNumber;           // 内部类       class SumCalculator implements Callable<Long> {           ......       }           public ConcurrentCalculator2() {           cpuCoreNumber = Runtime.getRuntime().availableProcessors();           exec = Executors.newFixedThreadPool(cpuCoreNumber);           completionService = new ExecutorCompletionService<Long>(exec);               }           public Long sum(final int[] numbers) {           // 根据CPU核心个数拆分任务，创建FutureTask并提交到Executor           for (int i = 0; i < cpuCoreNumber; i++) {               int increment = numbers.length / cpuCoreNumber + 1;               int start = increment * i;               int end = increment * i + increment;               if (end > numbers.length)                   end = numbers.length;               SumCalculator subCalc = new SumCalculator(numbers, start, end);                if (!exec.isShutdown()) {                   completionService.submit(subCalc);                       }                           }           return getResult();       }           /**       * 迭代每个只任务，获得部分和，相加返回       *        * @return       */      public Long getResult() {           Long result = 0l;           for (int i = 0; i < cpuCoreNumber; i++) {                           try {                   Long subSum = completionService.take().get();                   result += subSum;                          } catch (InterruptedException e) {                   e.printStackTrace();               } catch (ExecutionException e) {                   e.printStackTrace();               }           }           return result;       }           public void close() {           exec.shutdown();       }   }