e050. determining when the application is about to exit.txt

这里面包含了一百多个JAVA源文件

When an application is terminated normally, the application first starts any registered shutdown threads, waits for them to complete and then finally exits. Normal termination can be caused by a call to System.exit(), the completion of the last non-daemon thread, or the interruption of the application (control-C) by the user. Abnormal termination (which does not cause the shutdown threads to be started) is caused some major fault in the Java virtual machine or native library. 
    // Register a shutdown thread
    Runtime.getRuntime().addShutdownHook(new Thread() {
        // This method is called during shutdown
        public void run() {
            // Do shutdown work ...
        }
    });