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jijo
jijo

Reputation: 815

using numeric as enum key

Due to an unavoidable circumstance, I need to create an enum class like below,

public enum Region
{
 1("Region1"),
 2("Region2");
}

But I'm getting an error as "Syntax error on token '1', identifier expected". This enum is used in an option tag in jsp. It works fine if use a string instead of 1, enum doesn't allow numeric as keys ?

Upvotes: 0

Views: 1509

Answers (3)

Tunaki
Tunaki

Reputation: 137064

The first character of any identifier has to be a letter. From the JLS section 3.8 (emphasis mine):

An identifier is an unlimited-length sequence of Java letters and Java digits, the first of which must be a Java letter.

[...]

A "Java letter" is a character for which the method Character.isJavaIdentifierStart(int) returns true.

The "Java letters" include uppercase and lowercase ASCII Latin letters A-Z (\u0041-\u005a), and a-z (\u0061-\u007a), and, for historical reasons, the ASCII underscore (_, or \u005f) and dollar sign ($, or \u0024). The $ sign should be used only in mechanically generated source code or, rarely, to access pre-existing names on legacy systems.

Digits are not allowed, so you can't name your enum values 1 and 2.

Upvotes: 1

Reimeus
Reimeus

Reputation: 159754

Numbers are invalid as identifiers in Java. Typically uppercase letters are used when defining enum constants

Upvotes: 1

evanwong
evanwong

Reputation: 5134

No, you can't use numeric as the enum names. Maybe you can do 

public enum Region {
  ONE("region1"),
  TWO("region2");
}

Upvotes: 0

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