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個人理解 Future 模式就是在主線程中當需要進行比較耗時的作業，但不想阻塞主線程的作業時，將耗時作業交由 Future 對象在后臺中完成，當主線程將來（這個 Future 的意義也就體現在這里了）需要時即可通過 Future 對象獲得已經作業對象。 ?

這里寫了一個簡單的例子來說明這種模式，其實寫這個例子主要是自己想熟悉一下 JDK5 的 concurrency 包中 FutureTask 的用法了。例子模擬的是一個會計算賬的過程，主線程中已經獲得其他帳戶的總額了，為了不讓主線程等待 PrivateAccount 返回而啟用新的線程去處理，并使用 FutureTask 對象來監控，最后需要計算總額的時候再嘗試去獲得 PrivateAccount 的信息。

?

代碼如下：

?1 package ?testCallable;
?2
?3 import ?java.util.Random;
?4 import ?java.util.concurrent.Callable;
?5 import ?java.util.concurrent.ExecutionException;
?6 import ?java.util.concurrent.FutureTask;
?7
?8 /**?*/ /**
?9 ?*? @author ?chenpengyi
10 ? */
11 public ? class ?SumAccountExample? {
12
13 ???? public ? static ? void ?main(String[]?args)? {
14 ???????? // ?Init?callable?object?and?future?task
15 ????????Callable?pAccount? = ? new ?PrivateAccount();
16 ????????FutureTask?futureTask? = ? new ?FutureTask(pAccount);
17 ????????
18 ???????? // ?Create?a?new?thread?to?do?so
19 ????????Thread?pAccountThread? = ? new ?Thread(futureTask);
20 ????????pAccountThread.start();
21 ????????
22 ???????? // ?Do?something?else?in?the?main?thread
23 ????????System.out.println( " Doing?something?else?here. " );
24 ????????
25 ???????? // ?Get?the?total?money?from?other?accounts?
26 ???????? int ?totalMoney? = ? new ?Random().nextInt( 100000 );
27 ????????System.out.println( " You?have? " ? + ?totalMoney? + ? " ?in?your?other?Accounts. " );
28 ????????System.out.println( " Waiting?for?data?from?Private?Account " );
29 ???????? // ?If?the?Future?task?is?not?finished,?we?will?wait?for?it
30 ???????? while ( ! futureTask.isDone()) {
31 ???????????? try ? {
32 ????????????????Thread.sleep( 5 );
33 ????????????} ? catch ?(InterruptedException?e)? {
34 ????????????????e.printStackTrace();
35 ????????????}
36 ????????}
37 ????????Integer?privataAccountMoney? = ? null ;
38 ???????? // ?Since?the?future?task?is?done,?get?the?object?back
39 ???????? try ? {
40 ????????????privataAccountMoney? = ?(Integer)futureTask.get();
41 ????????} ? catch ?(InterruptedException?e)? {
42 ????????????e.printStackTrace();
43 ????????} ? catch ?(ExecutionException?e)? {
44 ????????????e.printStackTrace();
45 ????????}
46 ????????System.out.println( " The?total?moeny?you?have?is? " ? + ?(totalMoney? + ?privataAccountMoney.intValue()));
47 ????}
48
49 }
50
51
52 class ?PrivateAccount? implements ?Callable {
53
54 ????Integer?totalMoney;
55 ????
56 ????@Override
57 ???? public ?Integer?call()? throws ?Exception? {
58 ???????? // ?Simulates?a?time?conusimg?task,?sleep?for?10s
59 ????????Thread.sleep( 10000 );
60 ????????totalMoney? = ? new ?Integer( new ?Random().nextInt( 10000 ));
61 ????????System.out.println( " You?have? " ? + ?totalMoney? + ? " ?in?your?private?Account. " );
62 ???????? return ?totalMoney;
63 ????}
64 ????
65 }