免责声明:我什至没有尝试编译我的代码,但这种模式之前已经奏效了。
当我一眼看不到正则表达式的作用时,我会将其分成几行,以便更容易弄清楚发生了什么。不匹配的括号更明显,您甚至可以为其添加注释。另外,让我们在它周围添加 Java 代码,这样可以清楚地避免奇怪的东西。
^(\"[^,\"]*\")(,(\"[^,\"]*\"))*(.(\"[^,\"]*\")(,(\"[^,\"]*\")))*.$
变成
String regex = "^" +
"(\"[^,\"]*\")" +
"(," +
"(\"[^,\"]*\")" +
")*" +
"(." +
"(\"[^,\"]*\")" +
"(," +
"(\"[^,\"]*\")" +
")" +
")*" +
".$";
好多了。现在开始做生意:我看到的第一件事是引用值的正则表达式。它不允许在字符串中使用逗号——这可能不是你想要的——所以让我们解决这个问题。让我们也把它放在它自己的变量中,这样我们就不会在某些时候输入错误。最后,让我们添加注释,这样我们就可以验证正则表达式在做什么。
final String QUOTED_VALUE = "\"[^\"]*\""; // A double quote character, zero or more non-double quote characters, and another double quote
String regex = "^" + // The beginning of the string
"(" + QUOTED_VALUE + ")" + // Capture the first value
"(," + // Start a group, a comma
"(" + QUOTED_VALUE + ")" + // Capture the next value
")*" + // Close the group. Allow zero or more of these
"(." + // Start a group, any character
"(" + QUOTED_VALUE + ")" + // Capture another value
"(," + // Started a nested group, a comma
"(" + QUOTED_VALUE + ")" + // Capture the next value
")" + // Close the nested group
")*" + // Close the group. Allow zero or more
".$"; // Any character, the end of the input
事情变得更加清晰。我在这里看到两件大事:
1)(我认为)您正在尝试匹配输入字符串中的换行符。我会一起玩,但是在换行符上拆分输入比你正在做的更干净、更容易(不过,这是一个你可以自己做的练习)。您还需要注意不同操作系统具有的不同换行约定(阅读此内容)。
2)你捕捉的太多了。您想使用非捕获组或解析您的输出将变得困难且容易出错(阅读此内容)。
final String QUOTED_VALUE = "\"[^\"]*\""; // A double quote character, zero or more non-double quote characters, and another double quote
final String NEWLINE = "(\n|\n\r|\r\n)"; // A newline for (almost) any OS: Windows, *NIX or Mac
String regex = "^" + // The beginning of the string
"(" + QUOTED_VALUE + ")" + // Capture the first value
"(?:," + // Start a group, a comma
"(" + QUOTED_VALUE + ")" + // Capture the next value
")*" + // Close the group. Allow zero or more of these
"(?:" + NEWLINE + // Start a group, any character
"(" + QUOTED_VALUE + ")" + // Capture another value
"(?:," + // Started a nested group, a comma
"(" + QUOTED_VALUE + ")" + // Capture the next value
")" + // Close the nested group
")*" + // Close the group. Allow zero or more
NEWLINE + "$"; // A trailing newline, the end of the input
从这里,我看到你再次重复工作。让我们解决这个问题。这也修复了原始正则表达式中缺少的 *。看看你能不能找到它。
final String QUOTED_VALUE = "\"[^\"]*\""; // A double quote character, zero or more non-double quote characters, and another double quote
final String NEWLINE = "(\n|\n\r|\r\n)"; // A newline for (almost) any OS: Windows, *NIX or Mac
final String LINE = "(" + QUOTED_VALUE + ")" + // Capture the first value
"(?:," + // Start a group, a comma
"(" + QUOTED_VALUE + ")" + // Capture the next value
")*"; // Close the group. Allow zero or more of these
String regex = "^" + // The beginning of the string
LINE + // Read the first line, capture its values
"(?:" + NEWLINE + // Start a group for the remaining lines
LINE + // Read more lines, capture their values
")*" + // Close the group. Allow zero or more
NEWLINE + "$"; // A trailing newline, the end of the input
这更容易阅读,不是吗?现在,如果它不起作用,您可以分段测试您的大讨厌的正则表达式。
您现在可以编译正则表达式、获取匹配器并从中获取组。但是,您仍然有一些问题:
1)我之前说过,换行会更容易中断。一个原因是:你如何确定每行有多少个值?硬编码它会起作用,但一旦你的输入发生变化,它就会中断。也许这对您来说不是问题,但这仍然是不好的做法。另一个原因:正则表达式仍然太复杂,我不喜欢。你真的可以在 LINE 停下来。
2) CSV 文件允许这样的行:
"some text","123",456,"some more text"
要处理这个问题,您可能需要添加另一个获取引用值或数字列表的迷你正则表达式。