Ruby Bang Methods:
Methods which have ! sign at the end are called bang methods.
Standard Ruby bang methods often return nil if no change was needed.
str = 'FOOBAR' p str.upcase! #bang mehtod -> return nil p str.upcase # still return upcased string without any change p str arr = [1, 3, 7] p arr.uniq! #bang mehtod -> return nil p arr