如何使用空行拆分段落？答案

【问题标题】：How do I split the paragraph using empty lines?如何使用空行拆分段落？
【发布时间】：2016-04-23 19:41:12
【问题描述】：

我正在尝试使用 2 个空行来拆分段落。我尝试使用 String.split()、StringTokenizer 和 StringUtils 类，但没有一个有效。

这是我的代码：

   DeviceNames (interfacename) # show commands
   Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP
   O - OSPF, IA - OSPF inter area
   N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
   E1 - OSPF external type 1, E2 - OSPF external type 2
   i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter    area
   * - candidate default

  S*      0.0.0.0/0 [1/0] via 172.16.0.1, internal
  S       10.100.8.0/21 [10/0] is directly connected, vlink10
  C       0.0.2.0/24 is directly connected, internal
  C       0.0.2.0/24 is directly connected, wan1


  DeviceNames (interfacename) # show commands
  Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP
   O - OSPF, IA - OSPF inter area
   N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
   E1 - OSPF external type 1, E2 - OSPF external type 2
   i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
   * - candidate default

  S*      0.0.0.0/0 [10/0] is directly connected, vlink21
              [10/0] is directly connected, vlink30
  C       0.0.2.0/24 is directly connected, vlink30
  C       0.0.2.0/32 is directly connected, vlink30
  C       0.0.2.0/24 is directly connected, vlink21
  C       0.0.2.0/32 is directly connected, vlink21


  DeviceNames (interfacename) # show commands
  Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP
   O - OSPF, IA - OSPF inter area
   N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
   E1 - OSPF external type 1, E2 - OSPF external type 2
   i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
   * - candidate default

   S*      0.0.0.0/0 [10/0] is directly connected, vlink11
              [10/0] is directly connected, vlink31
   C       0.0.1.0/24 is directly connected, vlink31
   C       0.0.1.0.1.1/32 is directly connected, vlink31

我想像这样拆分上面的代码：

   DeviceNames (interfacename) # show commands
   Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP
   O - OSPF, IA - OSPF inter area
   N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
   E1 - OSPF external type 1, E2 - OSPF external type 2
   i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter    area
   * - candidate default

  S*      0.0.0.0/0 [1/0] via 172.16.0.1, internal
  S       10.100.8.0/21 [10/0] is directly connected, vlink10
  C       0.0.2.0/24 is directly connected, internal
  C       0.0.2.0/24 is directly connected, wan1

下一个：

   DeviceNames (interfacename) # show commands
  Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP
   O - OSPF, IA - OSPF inter area
   N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
   E1 - OSPF external type 1, E2 - OSPF external type 2
   i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
   * - candidate default

  S*      0.0.0.0/0 [10/0] is directly connected, vlink21
              [10/0] is directly connected, vlink30
  C       0.0.2.0/24 is directly connected, vlink30
  C       0.0.2.0/32 is directly connected, vlink30
  C       0.0.2.0/24 is directly connected, vlink21
  C       0.0.2.0/32 is directly connected, vlink21

下一个：

   DeviceNames (interfacename) # show commands
   Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP
   O - OSPF, IA - OSPF inter area
   N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
   E1 - OSPF external type 1, E2 - OSPF external type 2
   i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
   * - candidate default

   S*      0.0.0.0/0 [10/0] is directly connected, vlink11
              [10/0] is directly connected, vlink31
   C       0.0.1.0/24 is directly connected, vlink31
   C       0.0.1.0.1.1/32 is directly connected, vlink31

【问题讨论】：

标签： java regex parsing

【解决方案1】：

解决方案可以逐行读取文件并将每一行存储到变量（或数组，或您需要的）中。在阅读时，您可以通过以下方式检查该行是否为空行：

String newline = System.getProperty("line.separator"); // this is for getting proper new line;

boolean isNewline = myLine.startsWith(newline); //if your line start with newLine symbol

如果isNewLine 为真，那么你可以设置一个标志，如果下一行又是空的，那么你刚刚找到了你的段落。

【讨论】：

【解决方案2】：

String#split() 与正则表达式应该可以工作。

例如：

String[] paragraphs = input.split("\\n\\n\\n");

注意：这仅适用于 Unix 换行符。

【讨论】：

【解决方案3】：

您可以使用正则表达式将代码拆分为两个空行：

  public static void main(String[] args)
  {
    String str=" DeviceNames (interfacename) # show commands\n"+
" Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP\n"+
" O - OSPF, IA - OSPF inter area\n"+
" N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2\n"+
" E1 - OSPF external type 1, E2 - OSPF external type 2\n"+
" i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area\n"+
" * - candidate default\n"+
"\n"+
" S* 0.0.0.0/0 [1/0] via 172.16.0.1, internal\n"+
" S 10.100.8.0/21 [10/0] is directly connected, vlink10\n"+
" C 0.0.2.0/24 is directly connected, internal\n"+
" C 0.0.2.0/24 is directly connected, wan1\n"+
"\n"+
"\n"+
" DeviceNames (interfacename) # show commands\n"+
" Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP\n"+
" O - OSPF, IA - OSPF inter area\n"+
" N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2\n"+
" E1 - OSPF external type 1, E2 - OSPF external type 2\n"+
" i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area\n"+
" * - candidate default\n"+
"\n"+
" S* 0.0.0.0/0 [10/0] is directly connected, vlink21\n"+
" [10/0] is directly connected, vlink30\n"+
" C 0.0.2.0/24 is directly connected, vlink30\n"+
" C 0.0.2.0/32 is directly connected, vlink30\n"+
" C 0.0.2.0/24 is directly connected, vlink21\n"+
" C 0.0.2.0/32 is directly connected, vlink21\n"+
"\n"+
"\n"+
" DeviceNames (interfacename) # show commands\n"+
" Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP\n"+
" O - OSPF, IA - OSPF inter area\n"+
" N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2\n"+
" E1 - OSPF external type 1, E2 - OSPF external type 2\n"+
" i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area\n"+
" * - candidate default\n"+
"\n"+
" S* 0.0.0.0/0 [10/0] is directly connected, vlink11\n"+
" [10/0] is directly connected, vlink31\n"+
" C 0.0.1.0/24 is directly connected, vlink31\n"+
" C 0.0.1.0.1.1/32 is directly connected, vlink31\n"+
"";
    String[] array = str.split("(?<=\\S)\\n\\n\\n");

    for (int i = 0; i < array.length; i++) {
       System.out.println(String.format("================ %1$d ================\n%2$s", i + 1, array[i]));
       }  
    }

输出：

================ 1 ================
 DeviceNames (interfacename) # show commands
 Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP
 O - OSPF, IA - OSPF inter area
 N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
 E1 - OSPF external type 1, E2 - OSPF external type 2
 i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
 * - candidate default

 S* 0.0.0.0/0 [1/0] via 172.16.0.1, internal
 S 10.100.8.0/21 [10/0] is directly connected, vlink10
 C 0.0.2.0/24 is directly connected, internal
 C 0.0.2.0/24 is directly connected, wan1
================ 2 ================
 DeviceNames (interfacename) # show commands
 Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP
 O - OSPF, IA - OSPF inter area
 N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
 E1 - OSPF external type 1, E2 - OSPF external type 2
 i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
 * - candidate default

 S* 0.0.0.0/0 [10/0] is directly connected, vlink21
 [10/0] is directly connected, vlink30
 C 0.0.2.0/24 is directly connected, vlink30
 C 0.0.2.0/32 is directly connected, vlink30
 C 0.0.2.0/24 is directly connected, vlink21
 C 0.0.2.0/32 is directly connected, vlink21
================ 3 ================
 DeviceNames (interfacename) # show commands
 Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP
 O - OSPF, IA - OSPF inter area
 N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
 E1 - OSPF external type 1, E2 - OSPF external type 2
 i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
 * - candidate default

 S* 0.0.0.0/0 [10/0] is directly connected, vlink11
 [10/0] is directly connected, vlink31
 C 0.0.1.0/24 is directly connected, vlink31
 C 0.0.1.0.1.1/32 is directly connected, vlink31

【讨论】：

【解决方案4】：

这可以通过简单的正则表达式来完成：

试试：

 String[] paragraphs = text.split("(?im)(\r?\n){3,}");

变量text 包含您的数据。根据样本输入数据，上述语句将其分为 3 部分。此解决方案适用于在 Windows 或 Linux 上创建的文件，因此与平台无关。

【讨论】：