What is the contrast between poems?

The contrast method of poetry is to compare two opposite characters and things or two different aspects of the same character and thing to illustrate some truth. Contrast is also called "contrast". such as

Some people are alive and he is dead; Some people died, but he is still alive.

(Cang Kejia, "Some People")

Old people often think about the past, while young people often think about the future. (Liang Qichao's young chinese)

Comparing two completely opposite people, in sharp contrast, shows that some people are dead, but the people will always miss them; Although some people are alive, they are like walking dead, and the people hate them. Compare the different mental states of the old and the young, and form a sharp contrast to illustrate the following "conservative" and "enterprising" truth.