我想从spark中的字符串中提取一个特定的部分
例如，我的弦是

val b= "URL ftp://216.24.126.75/serversoftware/ocs/OCS_Inventory_NGInstallation_and_Administration_Guide_1.7_EN.odt
MENTION cryptography    201564  http://en.wikipedia.org/wiki/Cryptography
MENTION digital signature   201870  http://en.wikipedia.org/wiki/Digital_signature
TOKEN   decide  153579
TOKEN   Analyze 160938
TOKEN   properly    140437
TOKEN   reselect    78017
TOKEN   writing 60758 "

我想要这样的输出：

(ftp://216.24.126.75/serversoftware/ocs/OCS_Inventory_NGInstallation_and_Administration_Guide_1.7_EN.odt,http://en.wikipedia.org/wiki/Cryptography)
(ftp://216.24.126.75/serversoftware/ocs/OCS_Inventory_NGInstallation_and_Administration_Guide_1.7_EN.odt,http://en.wikipedia.org/wiki/Digital_signature)