Use Enum for keeping Constants [duplicate]

Question

I know the usage of enum in java.

Is recommended to use enums for storing the program constants(rather than the class described below)?

public class Constants{
    public static final String DB_CF_NAME = "agent";
    public static final String DB_CF_ID = "agent_id";
    public static final String DB_CF_TEXT = "agent_text";
    public static final String DB_CF_LATITUDE = "latitude";
}

Answer 1

It is recommended to use Enum. The possible reasons are like

• provides default functions to iterate through constants
• Can write static functions to get the values based on key

It is possible to make the methods by yourself, to make your class self sustained. but the preferable approach is using Enum

Answer 2

Yes, you're right - it is recommended to use enums for storing the program constants.

As you can see on examples below, this approach allows you to:

• add/override useful methods for your string literals:

  public enum Days {
      MONDAY("Monday"),
      TUESDAY("Tuesday"),
      SUNDAY ("Sunday");
  
  private final String name;
  
  private Day(String s) {
          name = s;
  }
  

• use built-in methods for Enums:

  public boolean equalsName(String otherName){
      return (otherName == null)? false : name.equals(otherName);
  }
  

• use EnumMap and EnumSet:

  private EnumSet<Option> badDays = EnumSet.of(Days.MONDAY, Days.TUESDAY);
  

Here is a good discussion about this.