ExecutorService invokeAll 实例

并发查询班级学生信息的Java多线程实现

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本文详细介绍了使用Java并发编程技术查询多个班级中学生信息的方法，通过创建自定义线程任务和利用Future接口实现了高效的数据查询。

10个班级，每个班级20名学生，在指定的时间内查询每个班级学生的集合。



package cn.com.ld.study.thread;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
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.TimeUnit;

public class FutureTest {
	//缓存操作数据集
	private static final Map<Integer, List<Student>> sutdenMap = new HashMap<Integer, List<Student>>();
	//初始化操作数据
	static {
		List<Student> stuList = null;
		Student stu;
		for (int i = 0; i < 10; i++) {
			stuList = new ArrayList<Student>();
			for (int j = 0; j < 2; j++) {
				stu = new Student(j, "zld_" + i + "." + j, i);
				stuList.add(stu);
			}
			sutdenMap.put(i, stuList);
		}
	}

	public static class Student {
		private int id;
		private String name;
		private int classID;

		public Student(int id, String name, int classID) {
			this.id = id;
			this.name = name;
			this.classID = classID;
		}

		public String toString() {
			return Student.class.getName() + "(id:" + this.id + ",name:"
					+ this.name + ")";
		}

	}

	/**   
	 * @filename: SearchTask   
	 * @description: 查询任务  
	 * @author lida  
	 * @date 2013-4-1 下午3:02:29      
	 */
	public static class SearchTask implements Callable<List<Student>> {

		public final int classID;
		public long sleepTime;

		/**   
		 * <p>Title: </p>   
		 * <p>Description: </p>   
		 * @param classID  班级编号
		 * @param sleepTime  模拟操作所用的时间数（毫秒）
		 */
		SearchTask(int classID, long sleepTime) {
			this.classID = classID;
			this.sleepTime = sleepTime;
		}

		@Override
		public List<Student> call() throws Exception {
			//模拟操作所用的时间数（毫秒）
			Thread.sleep(sleepTime);
			List<Student> stuList = sutdenMap.get(classID);
			return stuList;
		}

	}

	public static void main(String[] args) {
		FutureTest ft = new FutureTest();
		ExecutorService exec = Executors.newCachedThreadPool();
		List<SearchTask> searchTasks = new ArrayList<SearchTask>();
		SearchTask st;
		for (int i = 0; i < 10; i++) {
			st = new SearchTask(i, 2001);//指定2001 毫米为最大执行时间
			searchTasks.add(st);
		}

		try {
			//要求认为在2000毫秒内返回结果，否则取消执行。
			List<Future<List<Student>>> futures = exec.invokeAll(searchTasks,
					2000, TimeUnit.MILLISECONDS);//invokeAll 第一个参数是任务列表；第二个参数是过期时间；第三个是过期时间单位
			for (Future<List<Student>> future : futures) {
				List<Student> students = future.get();
				for (Student student : students) {
					System.out.println(student.toString());
				}
			}
			exec.shutdown();
		} catch (InterruptedException e) {
			e.printStackTrace();
			Thread.interrupted();
		} catch (ExecutionException e) {
			e.printStackTrace();
		}
	}
}