eixt()方法的说明：

public static void exit(int status)

Terminates the currently running Java Virtual Machine. The argument serves as a status code; by convention, a nonzero status code indicates abnormal termination.

This method calls the exit method in class Runtime. This method never returns normally.

The call System.exit(n) is effectively equivalent to the call:

Runtime.getRuntime().exit(n)

Parameters:

status - exit status.

Throws:

SecurityException - if a security manager exists and its checkExit method doesn’t allow exit with the specified status.

See Also:

Runtime.exit(int)

终止虚拟机的运行，其中，参数为0表示正常终止，参数非0为非正常终止。

[http://docs.oracle.com/javase/7/docs/api/java/lang/System.html#exit(int)]