The code example which can prove "volatile" declare should be used

Currently I can't understand when we should use volatile to declare variable.

I have do some study and searched some materials about it for a long time and know that when a field is declared volatile, the compiler and runtime are put on notice that this variable is shared and that operations on it should not be reordered with other memory operations.

However, I still can't understand in what scenario we should use it. I mean can someone provide any example code which can prove that using "volatile" brings benefit or solve problems compare to without using it?