In Java, variable names start with a letter, currency character ($) etc. but not with number, :, or .
Simple question: why is that?
Why doesn't the compiler allow to have variable declarations such as
int 7dfs;
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The downvote is probably a reflection of the poorly worded title, and the format of the question body. Do consider addressing those. – Bathsheba Jun 26 '17 at 13:45
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@Malinda You have asked a number of questions, if there are solutions which solve your problems, do consider accepting them. – user3437460 Jun 26 '17 at 14:13
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Because the language rules forbid it! See the JLS. – Lew Bloch Jun 26 '17 at 14:15
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This syntax detail of Java has been taken over from C++ and C (and possibly BCPL, I don’t know). It has also spread into many other langauges (not only C#). Since a lot of people know more than one language, a lot of people would be confused if the rules were changed. You *may* change the rules if you’ve got strong reasons; apparently they didn’t have here. – Ole V.V. Jun 26 '17 at 14:25
2 Answers
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Simply put, it would break facets of the language grammar.
For example, would 7f be a variable name, or a floating point literal with a value of 7?
You can conjure others too: if . was allowed then that would clash with the member selection operator: would foo.bar be an identifier in its own right, or would it be the bar field of an object instance foo?
Bathsheba
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Because the Java Language specification says so:
IdentifierChars:
JavaLetter {JavaLetterOrDigit}
So - yes, an identifier must start with a letter; it can't start with a digit.
The main reasons behind that:
- it is simply what most people expect
- it makes parsing source code (much) easier when you restrict the "layout" of identifiers; for example it reduces the possible ambiguities between literals and variable names.
