java - 如何使用 Java 正则表达式分割字符串，并在结果列表中包含可变宽度分隔符

Question

我想将字符串拆分为带引号和不带引号的部分，其中转义的引号将被忽略。例如，输入以下内容:

String input = "Example with \"quoted \\\"test\\\" region\" embedded";

应产生以下列表:

String[] result = ["Example with", "\"quoted \\\"test\\\" region\"", "embedded"];

为了分割引用区域(同时忽略转义引号)，我使用:

public static final String QUOTE_PATTERN = "(?<!\\\\)\".*?(?<!\\\\)\"";

String input = "Example with \"quoted \\\"test\\\" region\" embedded";
String[] result = input.split(QUOTE_PATTERN);
System.out.println(Arrays.toString(result));

它提供了预期的输出[带有嵌入的示例]。但是，我非常希望在此列表中也包含分隔符(引用的区域)。 (当然，我可以通过使用匹配器获取开始停止索引来实现这一点，但这仍然需要大量额外的代码。)

我找到了一个解决方案，通过使用前向和后向来拆分包含分隔符的字符串，它可以成功地将冒号分隔的字符串拆分为也包含冒号的列表:

public static final String WITH_DELIMITER = "((?<=%1$s)|(?=%1$s))";
public static final String COLON_PATTERN = String.format(WITH_DELIMITER, ":");

String colonTest = "Part0:Part1:Part2";
String[] parts = colonTest.split(COLON_PATTERN);

System.out.println(Arrays.toString(parts));

这提供了以下输出:[Part0, :, Part1, :, Part2]。

但是，这似乎不能应用于可变长度的分隔符，因为:

public static final String WITH_DELIMITER = "((?<=%1$s)|(?=%1$s))";
public static final String QUOTE_PATTERN = 
    String.format(WITH_DELIMITER, "(?<!\\\\)\".*?(?<!\\\\)\"");

String input = "Example with \"quoted \\\"test\\\" region\" embedded";
String[] result = input.split(QUOTE_PATTERN);
System.out.println(Arrays.toString(result));

抛出以下错误:

Exception in thread "main" java.util.regex.PatternSyntaxException: Look-behind group does not have an obvious maximum length near index 23
((?<=(?<!\\)".*?(?<!\\)")|(?=(?<!\\)".*?(?<!\\)"))
                   ^

有谁知道可变宽度分隔符是否可以实现类似的功能？

谢谢!

Answer 1

由于您的字符串长度不超过 200 个符号，因此您可以使用 Java constrained-width look-behind ，即 Java 的后视支持 {0,200}量词(其中指定最小和最大长度)。

✽ Java accepts quantifiers within lookbehind, as long as the length of the matching strings falls within a pre-determined range. For instance, (?<=cats?) is valid because it can only match strings of three or four characters. Likewise, (?<=A{1,10}) is valid.

因此，您可以利用此代码:

String.format(WITH_DELIMITER, "(?<!\\\\)\".{0,200}(?<!\\\\)\"");
                                           ^^^^^^^

参见IDEONE demo

   String WITH_DELIMITER = "((?<=%1$s)|(?=%1$s))";
   String QUOTE_PATTERN = 
   String.format(WITH_DELIMITER, "(?<!\\\\)\".{0,200}(?<!\\\\)\"");

   String input = "Example with \"quoted \\\"test\\\" region\" embedded";
   String[] result = input.split(QUOTE_PATTERN);
   System.out.println(Arrays.toString(result));

输出:

[Example with , "quoted \"test\" region",  embedded]