Java regex Matcher.matches 函数不匹配整个字符串答案

【问题标题】：Java regex Matcher.matches function does not match entire stringJava regex Matcher.matches 函数不匹配整个字符串
【发布时间】：2021-09-10 05:52:44
【问题描述】：

我正在尝试将整个字符串与正则表达式进行匹配，但即使整个字符串不匹配，Matcher.match 函数也会返回 true。

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Example {
    public static void main(String[] args) {
        final String string = "\"query1\" \"query2\" \"query3\"";
       // Unescaped Pattern: (\+?".*?[^\\]")(\s+[aA][nN][dD]\s+\+?".*?[^\\]")* 
       final Pattern QPATTERN = Pattern.compile("(\\+?\".*?[^\\\\]\")(\\s+[aA][nN][dD]\\s+\\+?\".*?[^\\\\]\")*", Pattern.MULTILINE);
        Matcher matcher = QPATTERN.matcher(string);
      
        System.out.println(matcher.matches());
        matcher = QPATTERN.matcher(string);  
        while (matcher.find()) {
            System.out.println("Full match: " + matcher.group(0));
            
            for (int i = 1; i <= matcher.groupCount(); i++) {
                System.out.println("Group " + i + ": " + matcher.group(i));
            }
        }
    }
}

您可以从 while 循环中看到，正则表达式仅匹配字符串 "query1" 、 "query2" 和 "query3" 的一部分，而不是整个字符串。然而，matcher.matches() 返回 true。

我哪里出错了？

我也检查了https://regex101.com/ 上的模式，整个字符串都不匹配。

【问题讨论】：

标签： java regex

【解决方案1】：

matches() 方法返回 true，因为它需要完整的字符串匹配。您说您在 regex101.com 上测试了正则表达式，但您忘记添加锚点来模拟 matches() 行为。

查看regex proof，您的正则表达式匹配整个字符串。

如果你想停止用这个表达式匹配整个字符串，不要使用.*?，这个模式可以匹配很多。

使用

(?s)(\+?\"[^\"\\]*(?:\\.[^\"\\]*)*\")(\s+[aA][nN][dD]\s+\+?\"[^\"\\]*(?:\\.[^\"\\]*)*\")*

转义版本：

String regex = "(?s)(\\+?\"[^\"\\\\]*(?:\\\\.[^\"\\\\]*)*\")(\\s+[aA][nN][dD]\\s+\\+?\"[^\"\\\\]*(?:\\\\.[^\"\\\\]*)*\")*";

解释

--------------------------------------------------------------------------------
  (?s)                     set flags for this block (with . matching
                           \n) (case-sensitive) (with ^ and $
                           matching normally) (matching whitespace
                           and # normally)
--------------------------------------------------------------------------------
  (                        group and capture to \1:
--------------------------------------------------------------------------------
    \+?                      '+' (optional (matching the most amount
                             possible))
--------------------------------------------------------------------------------
    \"                       '"'
--------------------------------------------------------------------------------
    [^\"\\]*                 any character except: '\"', '\\' (0 or
                             more times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
    (?:                      group, but do not capture (0 or more
                             times (matching the most amount
                             possible)):
--------------------------------------------------------------------------------
      \\                       '\'
--------------------------------------------------------------------------------
      .                        any character
--------------------------------------------------------------------------------
      [^\"\\]*                 any character except: '\"', '\\' (0 or
                               more times (matching the most amount
                               possible))
--------------------------------------------------------------------------------
    )*                       end of grouping
--------------------------------------------------------------------------------
    \"                       '"'
--------------------------------------------------------------------------------
  )                        end of \1
--------------------------------------------------------------------------------
  (                        group and capture to \2 (0 or more times
                           (matching the most amount possible)):
--------------------------------------------------------------------------------
    \s+                      whitespace (\n, \r, \t, \f, and " ") (1
                             or more times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
    [aA]                     any character of: 'a', 'A'
--------------------------------------------------------------------------------
    [nN]                     any character of: 'n', 'N'
--------------------------------------------------------------------------------
    [dD]                     any character of: 'd', 'D'
--------------------------------------------------------------------------------
    \s+                      whitespace (\n, \r, \t, \f, and " ") (1
                             or more times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
    \+?                      '+' (optional (matching the most amount
                             possible))
--------------------------------------------------------------------------------
    \"                       '"'
--------------------------------------------------------------------------------
    [^\"\\]*                 any character except: '\"', '\\' (0 or
                             more times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
    (?:                      group, but do not capture (0 or more
                             times (matching the most amount
                             possible)):
--------------------------------------------------------------------------------
      \\                       '\'
--------------------------------------------------------------------------------
      .                        any character
--------------------------------------------------------------------------------
      [^\"\\]*                 any character except: '\"', '\\' (0 or
                               more times (matching the most amount
                               possible))
--------------------------------------------------------------------------------
    )*                       end of grouping
--------------------------------------------------------------------------------
    \"                       '"'
--------------------------------------------------------------------------------
  )*                       end of \2 (NOTE: because you are using a
                           quantifier on this capture, only the LAST
                           repetition of the captured pattern will be
                           stored in \2)

【讨论】：

【解决方案2】：

当使用 grouping() 时，匹配项将被分成组，因此您永远不会将整个字符串放在一个组中。正则表达式本身看起来不错，但可能需要一些调整。这个帖子可能对你有帮助：Regex to find all matches

我也是新手，很抱歉无法提供更多帮助。

【讨论】：