Java-design pattern

Here,

anyone explain me about command and display design pattern?

Command pattern is a behavioural pattern meaning you will find verbs as class names in this code.these are also called Action/Transaction/Functor/Function Object.
To write a new operation don write a new method just create a class for same this is how its used typically in between view and controller.

This way of coding will alow to complete a transaction or rollback a transaction we can make it durable for doing database transaction we can use this way.