http://www.blogjava.net/zJun/archive/2006/03/12/34946.html

關閉鉤子”（ShutdownHook）是這樣一個概念：向虛擬機注冊一個線程，當程序退出(Ctrl+C)時虛擬機會啟動這個線程,我們可以在這個線程的run()中做一些清除的工作,如:釋放數據庫連接,關閉文件等.

注冊:

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Runtime.getRuntime().addShutdownHook(Thread?t);?

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注銷:

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Runtime.getRuntime().removeShutdownHook(Thread?t);

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[例子]

/**
?*?在這個線程中實現程序退出前的清理工作
?*?
?*?@author?Administrator
?*?
?*/
class?TestThread?extends?Thread?{
????boolean?isTerminal?=?false;

????public?void?run()?{
????????while?(!isTerminal)?{
???????????????try?{
??????????????????Thread.sleep(1000);
???????????????}?catch?(InterruptedException?e)?{
??????????????????e.printStackTrace();
???????????????}
????????????System.out.println("run?sub?thread");
????????}
????}

????/**//**
?????*?清理工作
?????*/
????public?void?onTerminal()?{
????????isTerminal?=?true;
????????System.out.println("stop?sun?sub?thread");
????}
}

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/**//**
?*?ShutdownDownHook測試類
?*?
?*?@author?Administrator
?*?
?*/
public?class?TestShutdownHook?extends?Thread?{
????TestThread?testThread;

????public?void?addThread(TestThread?t)?{
????????testThread?=?t;
????}

????/**//**
?????*?實現程序退出前的清理工作
?????*/
????public?void?run()?{
????????System.out.println("This?is?ShutdownHook");
????????testThread.onTerminal();
????}

????public?static?void?main(String[]?args)?{
????????TestShutdownHook?m?=?new?TestShutdownHook();
????????TestThread?t?=?new?TestThread();
????????t.start();
????????m.addThread(t);
????????//?注冊退出處理線程
????????Runtime.getRuntime().addShutdownHook(m);
????}
}

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運行結果:

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run?sub?thread
run?sub?thread
run?sub?thread
run?sub?thread
This?is?ShutdownHook
stop?sun?sub?thread

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可以看到:當程序退出時啟動了TestThread線程，執行了定義的釋放工作。

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