Java use user input to determine enum value

Question

I'm currently hardcoding an enum value, which is running through a switch statement. Is it possible to determine the enum based on user input.

Choice month = Choice.D;

Instead of hardcoding the value D, can I use the user input here?

package partyAffil;

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class partyAffil {

public static void main(String[] args) {
System.out.println("Choose from the following menu");
System.out.println("D, R, or I");   
String choice = getInput("please choose a letter.");


    Choice month = Choice.D;


    switch(month){ 
    case D:
        System.out.println("You get a Democratic Donkey");
        break;
    case R:
        System.out.println("You get a Republican Elephant");
        break;
    case I:
        System.out.println("You get an Independent Person");
        break;
    default:
        System.out.println("You get a unicorn");
        break;
        }
}

    public enum Choice{
        D, R, I;
    }

   private static String getInput(String prompt)
        {
        BufferedReader stdin = new BufferedReader(
                new InputStreamReader(System.in));
        System.out.print(prompt);
        System.out.flush();
        try{
            return stdin.readLine();
        } catch (Exception e){
            return "Error: " + e.getMessage();
        }
    }

}

Are you trying to create a initial menu for the user? where the user can choose from the list? — VD007
– VD007, Commented Jun 10, 2015 at 3:38
Possible duplicate: stackoverflow.com/questions/604424/… use Choice.valueOf — Radiodef
– Radiodef, Commented Jun 10, 2015 at 3:39

victordobry · Accepted Answer · 2015-06-10 04:25:53Z

3

Each enum constant have its own name as declared in its declaration. Static method valueOf of particular enum returns the enum constant of this type by name.

Thus, instead:

Choice month = Choice.D;

just use this:

Choice month = Choice.valueOf(choice);

edited Jun 10, 2015 at 4:25

answered Jun 10, 2015 at 3:51

victordobry

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Comments

NineToeNerd · Accepted Answer · 2015-06-10 03:51:46Z

0

What if you create the switch on the input rather than the month (or both, if they must be implemented separately)?:

Choice month;


switch(choice.toUpperCase()){ 
case 'D':
    month = Choice.D
    System.out.println("You get a Democratic Donkey");
    break;
    ...
    }

Better yet, I believe you could even set the character values in the enum:

public enum Choice{
        D('D'), R('R'), I('I');
    }

This way, instead of case 'D': you can still use case D:

(Not sure about that one, I am more used to C-based languages)

answered Jun 10, 2015 at 3:51

NineToeNerd

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Comments

VD007 · Accepted Answer · 2015-06-10 04:00:08Z

Above given answers might help. If you are not an expert, use following code that will you understand the steps.

    public void run() throws Exception
{
        switch (menu() ) //calling a menu method to get user input.
        {
            case 1:
              //fyi, make sure you have all the methods in your code that is given for each menu choice.
              //you can have print statement in your method.
                  // e.g.       System.out.println("You get a Democratic Donkey");
                method1();
                break;
            case 2:
                method2();
                break;
            case 3:
                method3();
                break;      
            case 0:
                return;  
            //following default clause executes in case invalid input is received.
            default:
                System.out.println ( "Unrecognized option" );
                break;
            }
}

private int menu()
{   
    //list of menu items.
    System.out.println ("1. insert appropriate description for your menu choice 1.");
    System.out.println ("2. ");
    System.out.println ("3. ");
    System.out.println ("4. ");
    return IO_Support.getInteger(">>    Select Option: ", "Unrecognized option"); //you can use scanner to get user input. I have user separate class IO_Support that has getInteger methods to validate int user input. the text "unrecognized option" is what the message that i want to print if the option is integer but not valid choice.
}

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