Type safety:unchecked cast from Object to ArrayList

It is not safe to show that the conversion of object to ArrayList is not secure.

When compiling, you need to add modifiers to compile correctly (specifically, the modifier). I don't remember. ^_^), otherwise you will be prompted with a warning

Of course, this is only a warning, if the landlord confident that the conversion is not a problem, you can add a note in front of the function
@SuppressWarnings ("uncheck")
This will remove the ugly hint of the warning yellow Line.

But do not encourage this, the landlord should still use a safe type conversion

Type safety:unchecked cast from Object to ArrayList