Variables names in Hex and Octal form

Hello,
Can we write a variable name with Hex or Octal notation ?

I tried the following.

int \u00C1 = 10;
int \u0041 = 15;
System.out.println("number is " + \u00C1);
System.out.println("number is " + \u0041);

and it works fine.
But when i tried to include the following statment the compiler throws me error.
int \101 = 10; //octal value for 'A'
Not sure why it is throwing error ? Does it mean we can write the variable name only through the octal representation ?

Thanks,
Mohamed

int \101 = 10; //octal value for 'A'

Well, no, that's the octal value for the number 10. Only numbers have octal representations in Java, and variable names can't be numbers. If you experiment further, you'll find that not all Unicode escapes can be variable names either. Only the ones that produce valid variable names work. For example you'll find that \u002e isn't a valid variable name... can you see why?

[Paul C]: Well, no, that's the octal value for the number 10. Only numbers have octal representations in Java, and variable names can't be numbers.

It looks to me like that's not an octal number, but an octal escape for character and String literals. Basically, things like 01, 053, 06235424 (0 followed by one or more octal digits) are octal integer literals, and represent numbers. Things like \123, \101, \012 are octal escapes for character and string literals, and can only appear inside quote marks, either single or double. Neither of these representations is allowed for other contexts such as identifiers.
[ January 28, 2008: Message edited by: Jim Yingst ]

Originally posted by Mohamed Alla Pitchai:
I tried the following.

int \u00C1 = 10;
int \u0041 = 15;
System.out.println("number is " + \u00C1);
System.out.println("number is " + \u0041);

and it works fine.
But when i tried to include the following statment the compiler throws me error.
int \101 = 10; //octal value for 'A'
Not sure why it is throwing error ?

You seem to be confused that unicode escapes and octal character escapes are treated differently in Java.

Well, don't be. If you check the JLS you'll see that they are indeed treated differently.

Unicode escapes are processed at an early stage and may occur anywhere in the source file. ("This translation step allows any program to be expressed using only ASCII characters." Unicode characters are allowed in Java comments, identifiers, character literals, and string literals.)

Octal character escapes are not processed early and may occur only in character and string literals.

Octal escapes... learn something new every day! Pity today's something-learned is so useless.

Perhaps worth making the point that naming variables like that, whether possible or not, is generally a very bad idea, because it makes the code much less readable.

Originally posted by David Payne:
Perhaps worth making the point that naming variables like that, whether possible or not, is generally a very bad idea, because it makes the code much less readable.

Ok, but let's be a little more precise. There's nothing wrong (case aside) with naming a variable A, and \u0041 is the same as A.

So in this case it's not the name of the variable that you would quibble with, but the style in which it was declared.

Now it's dumb to use \u0041 (since it's the same as A) but I see nothing wrong with naming a variable 中 if you speak Chinese and your editor can handle unicode: int 中 = 8;

If your editor can't handle unicode, then it would be dumb to write int \u4E2D = 8. You might as well just write int middle = 8 unless you need to do something like refer to a variable named in someone else's code.

Sorry Brian, you're absolutely right, of course - I should have thought more carefully about what I was objecting to

I did write a bleating comment about not using 中 as a variable name, or any other character that I'm too stupid to understand, but realised that my argument boiled down to just that - me being too stupid, so I've changed my mind