# File class/datedata.rb, line 19
        def read_file
                begin
                        fp = open(@file, "r")
                        fp.each {|line|
                                key, value = line.chomp.split(/\t/)
                                @date_data[key] = value
                        }
                        fp.close
                rescue
                        puts "'#{@file}' が見つかりません。"
                end
                not @date_data.empty? # データの有無(true/false)を返す
        end