Question

I have set of constants like:

public static final String CONST1="abc";
public static final String CONST2="cde";
public static final String CONST3="ftr";
...................................
public static final String CONSTN="zya";

In an application, I need to check if some value is in some set of constants, like:

if (String val in [CONST1,CONST2,CONST3]) {
do something;}
else {
....

Is it possible to do this with enum? Or is it better use a set or an array?
Thanks.

Answer 1

What you need is Enum.valueOf()

Returns the enum constant of the specified enum type with the
specified name. The name must match exactly an identifier used to
declare an enum constant in this type. (Extraneous whitespace
characters are not permitted.)

Here is an example of what I usually do when working with Enums and might have “bad” data coming in.

public class EnumTest
{
    public static void main(final String[] args)
    {
        final Option o = Option.safeValueOf(args[0]);
        switch(o)
        {
            case CHOICE_A: // fall through
            case CHOICE_B: // fall through
            case CHOICE_C: // fall through
                System.out.format("You selected %s", o );
                break;
            case CHOICE_D:
                System.out.format("You selected %s", o);
                break;
            default:
                System.out.format("Default Choice is %s", o );
        }
    }

    public enum Option
    {
        UNRECOGNIZED_CHOICE, CHOICE_A, CHOICE_B, CHOICE_C;

        // this hides the Exception handling code
        // so you don't litter your code with try/catch blocks
        Option safeValueOf(final String s)
        {
            try
            {
                return Option.valueOf(s);
            }
            catch (final IllegalArgumentException e)
            {
                return UNRECOGNIZED_CHOICE;
            }
        }
    }
}

you can also convert the Array of values from Option.values() into an EnumSet and search them and avoid the overhead of the possible Exception if you think it will be getting lots of bad data.