Returns a centered copy of self.

If integer argument size is greater than the size (in characters) of self, returns a new string of length size that is a copy of self, centered and padded on both ends with pad_string:

'hello'.center(10)       # => "  hello   "
'  hello'.center(10)     # => "   hello  "
'hello'.center(10, 'ab') # => "abhelloaba"
'тест'.center(10)        # => "   тест   "
'こんにちは'.center(10)    # => "  こんにちは   "

If size is not greater than the size of self, returns a copy of self:

'hello'.center(5)  # => "hello"
'hello'.center(1)  # => "hello"