JAVA多线程之Future的实际使用

水深无声 2022-06-07 06:13 275阅读 0赞

话不都说，这里直接贴出代码：

package com.whb.test;
    
    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 com.whb.demo.Student;
    public class FutureTest {
    	public static void main(String[] args) throws InterruptedException, ExecutionException {
    		List<Future<Student>> results = new ArrayList<Future<Student>>();
    		ExecutorService es = Executors.newCachedThreadPool();
    		List<Student> list = new ArrayList<Student>();
    		for (int i = 0; i < 10; i++) {
    			Student stu = new Student();
    			stu.setAge(i);
    			stu.setName("张三"+i);
    			list.add(stu);
    		}
    		for (Student student : list) {
    			results.add(es.submit(new TaskStuCallable(student)));
    		}
    		
    		for (Future<Student> res : results){
    			System.out.println(res.get().toString());
    			list.add(res.get());
    		}
    	}
    	
    	public static class TaskStuCallable implements Callable<Student> {
    		private Student stu;
    		public TaskStuCallable(Student stu) {
    			super();
    			this.stu = stu;
    		}
    		@Override
    		public Student call() throws Exception {
    			String tid = String.valueOf(Thread.currentThread().getId());
    			System.out.printf("Thread#%s : in call\n", tid);
    			stu.setAge(Integer.valueOf(tid));
    			stu.setName(stu.getName()+"----"+tid);
    			return stu;
    		}
    	}
    }

总结使用：此处使用的线程池是ExecutorService es = Executors.newCachedThreadPool();Future。但是也可以考虑使用

ExecutorService threadPool = Executors.newCachedThreadPool();
            CompletionService<Integer> cs = new ExecutorCompletionService<Integer>(threadPool);
            for(int i = 1; i < 5; i++) {
                final int taskID = i;
                cs.submit(new Callable<Integer>() {
                    public Integer call() throws Exception {
                        return taskID;
                    }
                });
            }
            for(int i = 1; i < 5; i++) {
                try {
                    System.out.println(cs.take().get());
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

CompletionService可以保证执行的顺便，但是Future好像也是可以保证顺序输出的。亲测如下：

Thread#10 : in call
    Thread#19 : in call
    Thread#18 : in call
    Student [age=10, name=张三0----10]
    Thread#17 : in call
    Thread#16 : in call
    Thread#15 : in call
    Thread#14 : in call
    Thread#13 : in call
    Thread#12 : in call
    Thread#11 : in call
    Student [age=11, name=张三1----11]
    Student [age=12, name=张三2----12]
    Student [age=13, name=张三3----13]
    Student [age=14, name=张三4----14]
    Student [age=15, name=张三5----15]
    Student [age=16, name=张三6----16]
    Student [age=17, name=张三7----17]
    Student [age=18, name=张三8----18]
    Student [age=19, name=张三9----19]

好了，这是我本地测试的结果。