Java并发编程之线程管理（Executor框架14）

4.4运行并发任务并返回所有运行结果

ThreadPoolExecutor提供了一个方法，它允许你发送给executor一列的任务链表，并且等待这些任务的终结。请看下面实例。

Result类的定义如下所示：

 

/** * This class stores the resultgenerated by one task * */public class Result {    /**     * The name of the task that generates theresult     */    private String name;    /**     * The value of the task that generates theresult     */    private intvalue;       /**     * Returns the name of the task     * @return Name of the task that generates the result     */    public String getName() {        return name;    }       /**     * Establish the name of the task     * @param name The name of the task that generates the result     */    public voidsetName(String name) {        this.name = name;    }       /**     * Returns the value of the result     * @return The value of the result     */    public intgetValue() {        return value;    }       /**     * Establish the value of the result     * @param value The value of the result     */    public voidsetValue(intvalue) {        this.value = value;    }   }

定义Task类，实现必要的逻辑。

 

import java.util.ArrayList;import java.util.List;import java.util.concurrent.Callable;importjava.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.Future;import java.util.concurrent.TimeUnit; /** * This class implements the task ofthis example. It waits during a random * period of time and then calculatethe sum of five random numbers * */public class Task implements Callable<Result> {     /**     * The name of the Task     */    private String name;       /**     * Constructor of the class     * @param name Initializes the name of the task     */    public Task(String name) {        this.name=name;    }       /**     * Main method of the task. Waits during arandom period of time and then     * calculates the sum of five random numbers     */    @Override    public Result call() throws Exception {        // Writes a message to the console        System.out.printf("%s: Staring\n",this.name);               // Waits during a random period of time        try {            Long duration=(long)(Math.random()*10);            System.out.printf("%s: Waiting %d seconds for results.\n",this.name,duration);            TimeUnit.SECONDS.sleep(duration);        } catch (InterruptedException e) {            e.printStackTrace();        }                     // Calculates the sum of five random numbers        int value=0;        for (int i=0; i<5; i++){            value+=(int)(Math.random()*100);         }               // Creates the object with the results        Result result=new Result();        result.setName(this.name);        result.setValue(value);        System.out.printf("%s: Ends\n",this.name);         // Returns the result object        return result;    }     public staticvoidmain(String []args){         // Create an executor        ExecutorServiceexecutor=(ExecutorService)Executors.newCachedThreadPool();         // Create three tasks and stores them in a List        List<Task> taskList=newArrayList<Task>();        for (int i=0; i<3; i++){            Task task=new Task("Task-"+i);            taskList.add(task);        }         // Call the invokeAll() method        List<Future<Result>>resultList=null;        try {            resultList=executor.invokeAll(taskList);        } catch (InterruptedException e) {            e.printStackTrace();        }        // Finish the executor        executor.shutdown();               // Writes the results to the console        System.out.printf("Core: Printing the results\n");        for (int i=0; i<resultList.size(); i++){            Future<Result>future=resultList.get(i);            try {                Result result=future.get();                System.out.printf("%s: %s\n",result.getName(),result.getValue());            } catch (Exception e) {                e.printStackTrace();            }        }    }   }

运行结果：

Task-0:StaringTask-2:StaringTask-1:StaringTask-2:Waiting 3 seconds for results.Task-0:Waiting 0 seconds for results.Task-1:Waiting 4 seconds for results.Task-0:EndsTask-2:EndsTask-1:EndsCore:Printing the resultsTask-0:175Task-1:206Task-2: 101