Why can't I use \u000D and \u000A as CR and LF in Java?

Question

Why can't I use \u000D and \u000A as CR and LF in Java? It's giving an error when I compile the code:

String x = "\u000A hello";//Error - Illegal escape character in string literal. 

Answer 1

Unicode escapes are pre-processed before the compiler is run. Therefore, if you put \u000A in a String literal like this:

String someString = "foo\u000Abar"; 

It will be compiled exactly as if you wrote:

String someString = "foo bar"; 

Stick to \r (carriage return; 0x0D) and \n (line feed; 0x0A)

Bonus: You can always have fun with this, especially given the limitations on most syntax highlighters. Next time you've got a sec, try running this code:

public class FalseIsTrue {     public static void main(String[] args) {         if ( false == true ) { //these characters are magic: \u000a\u007d\u007b             System.out.println("false is true!");         }     } } 

Answer 2

Because it falls within the range of Unicode Control characters

Which is U+0000–U+001F and U+007F.

Unicode control characters are used to control the interpretation or display of text, but these characters themselves have no visual or spatial representation.

They can be escaped by using \ like described in above answer by @Mark

FROM RFC:

2.5. Strings

The representation of strings is similar to conventions used in the C family of programming languages. A string begins and ends with quotation marks. All Unicode characters may be placed within the quotation marks except for the characters that must be escaped: quotation mark, reverse solidus, and the control characters (U+0000 through U+001F).

Any character may be escaped.