How to get value from a Java enum

Question

I have a enum which looks like:

public enum Constants{
  YES("y"), NO("N")
  private String value;

  Constants(String value){
    this.value = value;
  }
}

I have a test class which looks like

public class TestConstants{
 public static void main(String[] args){
   System.out.println(Constants.YES.toString())
   System.out.println(Constants.NO.toString())
 }
}

The output is:

YES
NO

instead of

Y
N

I am not sure what is wrong here ??

why do you expect that toString() returns the value?

wero
– wero

2016-02-01 21:24:50 +00:00
Commented Feb 1, 2016 at 21:24 — wero
– wero, Commented Feb 1, 2016 at 21:24

Mohammed Aouf Zouag · Accepted Answer · 2016-02-01 21:11:56Z

39

You need to override the toString method of your enum:

public enum Constants{
    YES("y"), NO("N")

    // No changes

    @Override
    public String toString() {
        return value;
    }
}

answered Feb 1, 2016 at 21:11

Mohammed Aouf Zouag

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10 Comments

Jim Garrison Over a year ago

Maybe, maybe not. Maybe the OP needs a separate getValue() method instead?

Mohammed Aouf Zouag Over a year ago

Maybe, but the OP is explicitly calling the un-overriden toString() method of his enum, which pretty much sums it all.

Mandar Over a year ago

What is a better practice. Overriding the toString() method or writing a separate getter method ??

m.aibin Over a year ago

getter method is simplier, but both of solutions are ok.

hfontanez Over a year ago

Although this solution works, it only works for this SPECIFIC problem. If a "googler" comes here and the enum he or she needs to obtain the value from has non-String values, this solution will not work. As as common practice, you should not use the toString() to return values. That violates the Object.toString() API. In addition, overriding this method works only for String values. Instead, you should create a getValue() function that returns the appropriate data type. See David Yee's or Just a Logic Gate's answer. They are more correct than this one, regardless of the OPs vote.

|

David Yee · Accepted Answer · 2016-02-01 21:15:28Z

17

You can also add a getter to the enumeration and simply call on it to access the instance variable:

public enum Constants{
    YES("Y"), NO("N");
    private String value;

    public String getResponse() {
        return value;
    }

    Constants(String value){
        this.value = value;
    }
}

public class TestConstants{
    public static void main(String[] args){
        System.out.println(Constants.YES.getResponse());
        System.out.println(Constants.NO.getResponse());
    }
}

answered Feb 1, 2016 at 21:15

David Yee

3,67628 silver badges48 bronze badges

1 Comment

hfontanez Over a year ago

Regardless of the OP's vote, this is the correct solution. See my comment in the "Best Answer" post.

Just a Logic Gate · Accepted Answer · 2016-02-01 21:49:36Z

12

Create a getValue() method in your enum, and use this instead of toString().

public enum Constants{
 YES("y"), NO("N")
 private String value;

 Constants(String value){
  this.value = value;
 }
}

 public String getValue(){
  return value;
 }

And instead of:

System.out.println(Constants.YES.toString())
System.out.println(Constants.NO.toString())

(Which are also missing a semi-colon), use

System.out.println(Constants.YES.getValue());
System.out.println(Constants.NO.getValue());

Hope this solved your problem. If you do not want to create a method in your enum, you can make your value field public, but this would break encapsulation.

answered Feb 1, 2016 at 21:49

Just a Logic Gate

1337 bronze badges

1 Comment

hfontanez Over a year ago

Regardless of the OP's vote, this is the correct solution. See my comment in the "Best Answer" post.

m.aibin · Accepted Answer · 2016-02-01 21:11:34Z

7

Write Getter and Setter for value and use:

System.out.println(Constants.YES.getValue());
System.out.println(Constants.NO.getValue());

answered Feb 1, 2016 at 21:11

m.aibin

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Comments

Peter · Accepted Answer · 2018-06-08 10:56:22Z

0

String enumValue = Constants.valueOf("YES")

Java doc ref: https://docs.oracle.com/javase/7/docs/api/java/lang/Enum.html#valueOf(java.lang.Class,%20java.lang.String)

answered Jun 8, 2018 at 10:56

Peter

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1 Comment

hfontanez Over a year ago

Why use valueOf? This is more error prone than to use the enum itself and call its getter method.

anand krish · Accepted Answer · 2023-04-10 16:24:40Z

0

The elegant way to get value of an Enum is by using ordinal method.

public enum Constants
{
  YES("Y"), NO("N");
  private String value;

public String getResponse() {
    return value;
}

Constants(String value){
    this.value = value;
}
public static Constants getConstants(int value){
    for(Constants e : Constants.values()){
        if(value == e.getResponse()) return e;
    }
    return null;
  }
}

public class TestConstants{
public static void main(String[] args)
  {
    System.out.println(Constants.YES.ordinal());
    System.out.println(Constants.NO.ordinal());
  }
}

answered Apr 10, 2023 at 16:24

anand krish

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