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From: Knute Johnson <nospam@knutejohnson.com>
Newsgroups: comp.lang.java.programmer
Subject: Re: unicode
Date: Mon, 12 Sep 2011 14:04:13 -0700
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On 9/12/2011 12:24 PM, bob wrote:
> Why does Java complain when I do this?
>
> 	html = html.replaceAll("\u000A", " ");
>
> This one works:
>
> 		// nbsp
> 		html = html.replaceAll("\u00A0", " ");


That was interesting.  From the docs on java.util.regex.Pattern;

"Comparison to Perl 5

The Pattern engine performs traditional NFA-based matching with ordered 
alternation as occurs in Perl 5.

Perl constructs not supported by this class:
     .
     .
     .
     The preprocessing operations \l \u, \L, and \U."

You can however do this, which is even more interesting!

public class test {
     public static void main(String[] args) {
         String html = "hello world!\n";
         html = html.replaceAll("\\x{a}","~");
         System.out.println(html);
     }
}

C:\Documents and Settings\Knute Johnson>java test
hello world!~

 From the Java Language Specification

"Because Unicode escapes are processed very early, it is not correct to 
write "\u000a" for a string literal containing a single linefeed (LF); 
the Unicode escape \u000a is transformed into an actual linefeed in 
translation step 1 (§3.3) and the linefeed becomes a LineTerminator in 
step 2 (§3.4), and so the string literal is not valid in step 3. 
Instead, one should write "\n" (§3.10.6). Similarly, it is not correct 
to write "\u000d" for a string literal containing a single carriage 
return (CR). Instead use "\r"."

And there you have it!

-- 

Knute Johnson