Introducing Java, Models, and Various Framework articles, often use metaphors, metaphor, and as the name implies are not very straightforward. Why is "not straight-white"? The reasons are two: (1), some people like to happen, such as "Tianwang Gen Tiger". Said valeries, elegant, professional, like to create many new vocabulary, long time, metaphor has become the most straightforward vocabulary, such as (Pojo, IOC). (2) itself is less accurately metaphor. In the morning, I suddenly remembered the last time I went to Shanghai, I took a taxi together with my friends. Freeagle said to the driver: "Zunyi Road, Yuping South Road.", Then explained to me: "Shanghai talks about the destination, report two The road name can be "." Mathematical two-wire cross can be fixed! accurate! Smart Shanghai people! So if we don't very clear in a metaphor (Metaphor), we use two different directions, which should be relatively clearly expressed. If you create a "happen", call it "M2". how is it? "Baota Town Group!"