class RuboCop::Cop::Style::EmptyLineBetweenDefs

separated by empty lines.
This cop checks whether method definitions are

def autocorrect(node) 

def autocorrect(node)
  range = range_with_surrounding_space(node.loc.expression, :left)
  @corrections << lambda do |corrector|
    corrector.insert_before(range, "\n")
  end
end

def def_end(node) 

def def_end(node)
  node.loc.end.line
end

def def_start(node) 

def def_start(node)
  node.loc.keyword.line
end

def on_def(node) 

def on_def(node)
  if @prev_def_end && (def_start(node) - @prev_def_end) == 1
    unless @prev_was_single_line && singe_line_def?(node) &&
           cop_config['AllowAdjacentOneLineDefs']
      add_offense(node, :keyword)
    end
  end
  @prev_def_end = def_end(node)
  @prev_was_single_line = singe_line_def?(node)
end

def singe_line_def?(node) 

def singe_line_def?(node)
  def_start(node) == def_end(node)
end