参考文档:
Java多线程编程模式实战指南之Promise模式
今天看到《
Java多线程编程模式实战指南之Promise模式
》这篇文章,感觉不错,虽然以前也了解过 future 这个东东,但是理解不是那么深,联想起 jQuery 的 promise,决定按文档的代码尝试一下。下面粘出代码:
package com.yuzx.test.promise;
import org.junit.Test;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.FutureTask;
/**
* Created by yuzx on 15-12-11.
*/
public class PromiseTestMain {
private static class FtpClient {
private FtpClient() {
}
public static Future<FtpClient> newFtpClient(final String serverName, final String username, final String password) {
Callable<FtpClient> callable = new Callable<FtpClient>() {
@Override
public FtpClient call() throws Exception {
System.out.println("work 1.");
FtpClient ftpClient = new FtpClient();
ftpClient.init(serverName, username, password);
return ftpClient;
}
};
FutureTask<FtpClient> promise = new FutureTask<FtpClient>(callable);
new Thread(promise).start();
// 先给个承诺,将来拿这个承诺来找我
return promise;
}
private void init(String serverName, String username, String password) throws InterruptedException {
Thread.sleep(5000);
}
private void printWork2(int res) {
System.out.println("res is " + res);
}
}
// 另一件很费时的任务
private int work2() throws InterruptedException {
System.out.println("work 2.");
Thread.sleep(3000);
return 109;
}
/**
* 将耗时操作均封装为 Promise,并行执行耗时操作
*
* @throws InterruptedException
* @throws ExecutionException
*/
@Test
public void doTest() throws InterruptedException, ExecutionException {
Future<FtpClient> promise = FtpClient.newFtpClient("10.0.3.242", "yuzx", "pAs$w0rd");
int res = work2();
promise.get().printWork2(res);
FtpClient ftpClient = null;
try {
// 获取初始化完毕的FTP客户端实例
ftpClient = promise.get();
} catch (InterruptedException e) {
;
} catch (ExecutionException e) {
throw new RuntimeException(e);
}
}
}
可以将耗时的操作都封装为 promise,并行执行 Task,那么整个 Job 所花的时间应该是耗时最长的 Task 的时间,而不是所有 Task 的时间和。
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