java线程处理问题

Java code:

public class Outdb extends Thread implements SignalHandler {
........................
........................

private void signalCallback(Signal sn) {
System.out.println(sn.getName() + "is recevied.");
System.out.println("-----------------------------");
System.out.println("SINGAL:" + Thread.activeCount());
System.exit(0);
}

public void run() {
System.out.println("-----------------------------");
System.out.println("addShutdownHook run:" + Thread.activeCount());
appExit();
}

/**
* @重写信号处理函数
* @说明：当接收信号时调用调用信号处理函数
* @Date : 2010-02-01
* @param: 注册信号名称
*/
public void handle(Signal signalName) {
signalCallback(signalName);
// Chain back to previous handler, if one exists
if (oldHandler != SIG_DFL && oldHandler != SIG_IGN) {
System.out.println("another signal received , Chain back!");
oldHandler.handle(signalName);
}

}

/**
* @Main 主函数
* @Date : 2010-02-01
* @param: param 程序调用参数数组
*/
public static void main(String param[]) throws Exception {
Outdb doit = new Outdb();