Unexpected Token - Java Enum-CodePudding

Is there any option in java to Create an enum with true and false like below,

public enum options {
true,
false,
both
}

Now getting unexpected token error as I am using true and false. thank you

Regards haru

CodePudding user response：

No. From JLS 8.9.1, an enum constant is defined in the syntax to be

EnumConstant:
    {EnumConstantModifier} Identifier [( [ArgumentList] )] [ClassBody]

So it's an Identifier. And from JLS 3.8, and Identifier is defined to be

Identifier:
    IdentifierChars but not a Keyword or BooleanLiteral or NullLiteral

Hence, an identifier is any valid string of identifier characters (basically letters and numbers, but with Unicode support thrown in) that is not a keyword (like if) or the words true, false, or null.

Realistically, you should be capitalizing your enum names anyway, so it would look more like

public enum Options {
  TRUE, FALSE, BOTH
}

which poses no issues as TRUE and FALSE aren't Boolean literals in Java.

CodePudding user response：

The values of your enum should be formatted like constants; all-caps with underscores between words (if they are more than one word, which in your case, they are not). If you need to be able to convert them to/from strings that do not match the name and case of the enum constants, I would suggest adding a parameter with the string and methods to convert in each direction:

public enum Options {
    TRUE("true"),
    FALSE("false"),
    BOTH("both");
    
    private final String description;
    
    private Options(final String description) {
        this.description = description;
    }
    
    public String getDescription() {
        return description;
    }
    
    public static Options parse(String description) {
        for (Options option : Options.values()) {
            if (option.getDescription().equals(description)) {
                return option;
            }
        }
        throw new IllegalArgumentException("no such option: "   description);
    }
}

If you call Options.parse("true") it will return Options.TRUE and if you call Options.TRUE.getDescription() it will return "true". If you call Options.parse("none") it will throw an IllegalArgumentException.