unicode正则表达式模式不起作用

Question

I am trying to match some unicode charaters sequence:

Pattern pattern = Pattern.compile("\\u05[dDeE][0-9a-fA-F]{2,}");
    String text = "\\n     \\u05db\\u05d3\\u05d5\\u05e8\\u05d2\\u05dc\\n    <\\/span>\\n<br style=\\";
    Matcher match = pattern.matcher(text);

but doing so gives this exception:

Exception in thread "main" java.util.regex.PatternSyntaxException: Illegal Unicode escape sequence near index 4
  \u05[dDeE][0-9a-fA-F]+
      ^

how can I use still use regex with some regex chars (like "[") to match unicode?

EDIT: I'm trying to parse some text. The text somewhere has a sequence of Unicode characters, which I know their code range.

Edit2: I am now using ranges instead : [\\\א-\\\ת]{2,} but still can't match the text above

Edit3: ok, now it's working, the problem was I used two backslashes instead of one , both in the regex and text. The solution for this is, assuming I know there will be two chars or more:

[\u05d0-\u05ea]{2,}

Answer 1

Here is what causing the exception:

\\u05[dDeE][0-9a-fA-F]}{2,}
  ^^^^

The java regular expression parser thinks you are trying to match a Unicode code point using the escape sequence \\uNNNN so it is giving an exception, because \\u\u003c/code> requires four hexadecimal digits after it and there is only two of them, namely 05 so you need to change it to \\\ if that is what you actually want.

On the other hand, if you want to match \\\\u\u003c/code> in the target string, then you need to quad escape each backslash \\ like this \\\\\\\\ so to match \\\\u\u003c/code> you need \\\\\\\\\\\\\\\\u\u003c/code> .

\\\\\\\\u05[dDeE][0-9a-fA-F]}{2,}

Finally, if you want to match those Unicode code points literally in your target string then you need to modify our last expression a bit like this:

(?:\\\\\\\\u05[dDeE][0-9a-fA-F]){2,}

Edit: Since there is only one backslash in your target string then your regular expression should be:

(?:\\\\u05[dDeE][0-9a-fA-F]){2,}

This will match \כ\ד\ו\ר\ג\ל in your string

<\/span><\/span><span dir=\"rtl\">\n \u05db\u05d3\u05d5\u05e8\u05d2\u05dc\n <\/span>\n<br style=\"clear : both; font-size : 1px;\">\n<\/div>"}, 200, null, null);

Edit 2: If you want to match literal \כ\ד\ו\ר\ג\ל then you can't use a range.

On the other hand, if you want to match Unicode code points between 05d0 and 05df then you can use:

(?:[\\u05d0\\u05df]){2,}

Answer 2

It's not clear what you're trying to do. If your goal is to simplify matching a range of Unicode characters, then you need to realize that the hex digits are completely case insensitive, and so your a-fA-F is redundant, even if you could split character literals. Try this to match all Unicode characters in the range:

[\\u05d0-\\u0eff]

Answer 3

Looks like you have unnecessary \\\\ in your input string. Following works by replacing your specified unicode character range in regex:

String text = "\n  \u05db\u05d3\u05d5\u05e8\u05d2\u05dc\n    </span>\n<br style=\\";
System.out.println(text.replaceAll("[\u05d0-\u05ea]{2,}", "@@@"));

OUTPUT:

  @@@
    </span>

Note that in our input text you had \\\\n and \\\כ etc that I have fixed.