java - 在引号外用逗号分割

Question

我的程序从文件中读取一行。该行包含逗号分隔的文本，例如:

123,test,444,"don't split, this",more test,1

我希望分割的结果是这样的:

123
test
444
"don't split, this"
more test
1

如果我使用String.split(",")，我会得到这个:

123
test
444
"don't split
 this"
more test
1

换句话说:子字符串“don't split, this”中的逗号不是分隔符。怎么处理这个问题？

Answer 1

您可以尝试这个正则表达式:

str.split(",(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)");

这会在 , 上分割字符串，后跟偶数个双引号。换句话说，它在双引号外以逗号分隔。如果您的字符串中有平衡的引号，这将起作用。

说明:

,           // Split on comma
(?=         // Followed by
   (?:      // Start a non-capture group
     [^"]*  // 0 or more non-quote characters
     "      // 1 quote
     [^"]*  // 0 or more non-quote characters
     "      // 1 quote
   )*       // 0 or more repetition of non-capture group (multiple of 2 quotes will be even)
   [^"]*    // Finally 0 or more non-quotes
   $        // Till the end  (This is necessary, else every comma will satisfy the condition)
)

您甚至可以在代码中输入这样的内容，使用 (?x) 修饰符和正则表达式。修饰符会忽略正则表达式中的任何空格，因此更容易阅读分成多行的正则表达式，如下所示:

String[] arr = str.split("(?x)   " + 
                     ",          " +   // Split on comma
                     "(?=        " +   // Followed by
                     "  (?:      " +   // Start a non-capture group
                     "    [^\"]* " +   // 0 or more non-quote characters
                     "    \"     " +   // 1 quote
                     "    [^\"]* " +   // 0 or more non-quote characters
                     "    \"     " +   // 1 quote
                     "  )*       " +   // 0 or more repetition of non-capture group (multiple of 2 quotes will be even)
                     "  [^\"]*   " +   // Finally 0 or more non-quotes
                     "  $        " +   // Till the end  (This is necessary, else every comma will satisfy the condition)
                     ")          "     // End look-ahead
                         );