java - 正则表达式 :match string containing only non repeating words

Question

我有这种情况(Java代码):1) 一个字符串，如:“A wild adventure”应该匹配。2) 带有相邻重复词的字符串:“A wild wild adventure”不应该匹配。

使用这个正则表达式:.*\b(\w+)\b\s*\1\b.* i 可以匹配包含相邻重复单词的字符串。

如何扭转这种情况，即如何匹配不包含相邻重复词的字符串

Answer 1

使用否定先行断言，(?!pattern)。

    String[] tests = {
        "A wild adventure",      // true
        "A wild wild adventure"  // false
    };
    for (String test : tests) {
        System.out.println(test.matches("(?!.*\\b(\\w+)\\s\\1\\b).*"));
    }

解释由 Rick Measham's explain.pl 提供:

REGEX: (?!.*\b(\w+)\s\1\b).*
NODE                     EXPLANATION
--------------------------------------------------------------------------------
  (?!                      look ahead to see if there is not:
--------------------------------------------------------------------------------
    .*                       any character except \n (0 or more times
                             (matching the most amount possible))
--------------------------------------------------------------------------------
    \b                       the boundary between a word char (\w)
                             and something that is not a word char
--------------------------------------------------------------------------------
    (                        group and capture to \1:
--------------------------------------------------------------------------------
      \w+                      word characters (a-z, A-Z, 0-9, _) (1
                               or more times (matching the most
                               amount possible))
--------------------------------------------------------------------------------
    )                        end of \1
--------------------------------------------------------------------------------
    \s                       whitespace (\n, \r, \t, \f, and " ")
--------------------------------------------------------------------------------
    \1                       what was matched by capture \1
--------------------------------------------------------------------------------
    \b                       the boundary between a word char (\w)
                             and something that is not a word char
--------------------------------------------------------------------------------
  )                        end of look-ahead
--------------------------------------------------------------------------------
  .*                       any character except \n (0 or more times
                           (matching the most amount possible))

另见

• regular-expressions.info/Lookarounds

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---

注意事项

否定断言只有在还有其他您想要肯定匹配的模式时才有意义(参见上面的示例)。否则，您可以只使用 boolean 补码运算符 ! 来否定与您之前使用的任何模式的匹配。

String[] tests = {
    "A wild adventure",      // true
    "A wild wild adventure"  // false
};
for (String test : tests) {
    System.out.println(!test.matches(".*\\b(\\w+)\\s\\1\\b.*"));
}