unicode escapes

[Abu Yoosuf]

JLS 3.3
The character produced by a Unicode escape does not participate in further
Unicode escapes. For example, the raw input \u005cu005a results in the six char-acters
\ u 0 0 5 a, because 005c is the Unicode value for \.

I tried to test the following code snippet, but fails with "illegal escape character".

 
public static void main(String[] args)
{
   String s = "\u005cu005a";
   //                ^ -- error msg points 
   //to the position marked by ^.
   System.out.println(s);
}
 

What am I missing? Would appreciate any clarifications. Thanks.

[James Chegwidden]

You have to many characters in the sequence. That's whay it has an error.

[Abu Yoosuf]

James,
Are you disagreeing with what is in jls 3.3?
I tried few few other variations.
1. String s = "\u005c\u005a"; //doesn't compile
2. String ss = "\\u005c\u005a"; //output is \u005cZ
3. String sss = "\u005c\\u005a"; //output is \Z
I can understand the output for 2 & 3 but not for 1. If \u005c translates to \, I expected s to be assigned to "\\u005a" by the end of the translation.

[Jose Botella]

This is from JLS 3.10.6
(within an string literal..)

...It is a compile-time error if the character following a backslash in an escape is not
an ASCII b, t, n, f, r, ", ', \, 0, 1, 2, 3, 4, 5, 6, or 7. The Unicode escape \u is processed earlier

The following string is ok:
"\u005ctThis would be printed at a tab distance"
this string is equivalent to "\tThis would be..."
because \u005c has been translated to a backslash
However being \u0009 the Unicode for \t ,
"\u005cu0009Error"
will cause a compiler error, because \u005c has been translated to "\" and you cannot have "\u" within a string literal.

[Abu Yoosuf]

Thanks.