jcommander 解析boolean参数

boolean类型有点特殊，后面不需要跟一个值，输入-local之后，local值即为true：

@Parameter(names = { "-local"}, description = "Local model, default cluster Model.")
public static boolean LOCAL_MODE = false;

如果一个boolean变量的默认值为true，而想通过参数设置为false，可以指定元数：

@Parameter(names = { "-log", "-verbose"}, description = " Wheather to write system log.", arity = 1)
public static boolean LOG = true;