Using Enum values as String literals

What is the best way to use the values stored in an Enum as String literals? For example:

public enum Modes {
    some-really-long-string,
    mode1,
    mode2,
    mo开发者_如何学Pythonde3
}

Then later I could use Mode.mode1 to return its string representation as mode1. Without having to keep calling Mode.mode1.toString().

You can't. I think you have FOUR options here. All four offer a solution but with a slightly different approach...

Option One: use the built-in name() on an enum. This is perfectly fine if you don't need any special naming format.

    String name = Modes.mode1.name(); // Returns the name of this enum constant, exactly as declared in its enum declaration.

Option Two: add overriding properties to your enums if you want more control

public enum Modes {
    mode1 ("Fancy Mode 1"),
    mode2 ("Fancy Mode 2"),
    mode3 ("Fancy Mode 3");

    private final String name;       

    private Modes(String s) {
        name = s;
    }

    public boolean equalsName(String otherName) {
        // (otherName == null) check is not needed because name.equals(null) returns false 
        return name.equals(otherName);
    }

    public String toString() {
       return this.name;
    }
}

Option Three: use static finals instead of enums:

public final class Modes {

    public static final String MODE_1 = "Fancy Mode 1";
    public static final String MODE_2 = "Fancy Mode 2";
    public static final String MODE_3 = "Fancy Mode 3";

    private Modes() { }
}

Option Four: interfaces have every field public, static and final:

public interface Modes {

    String MODE_1 = "Fancy Mode 1";
    String MODE_2 = "Fancy Mode 2";
    String MODE_3 = "Fancy Mode 3";  
}

Every enum has both a name() and a valueOf(String) method. The former returns the string name of the enum, and the latter gives the enum value whose name is the string. Is this like what you're looking for?

String name = Modes.mode1.name();
Modes mode = Modes.valueOf(name);

There's also a static valueOf(Class, String) on Enum itself, so you could also use:

Modes mode = Enum.valueOf(Modes.class, name);

You could override the toString() method for each enum value.

Example:

public enum Country {

  DE {
    @Override
    public String toString() {
      return "Germany";
    }
  },
  IT {
    @Override
    public String toString() {
      return "Italy";
    }
  },
  US {
    @Override
    public String toString() {
      return "United States";
    }
  }

}

Usage:

public static void main(String[] args) {
  System.out.println(Country.DE); // Germany
  System.out.println(Country.IT); // Italy
  System.out.println(Country.US); // United States
}

As Benny Neugebauer mentions, you could overwrite the toString(). However instead overwriting the toString for each enum field I like more something like this:

public enum Country{
    SPAIN("España"),
    ITALY("Italia"),
    PORTUGAL("Portugal");


    private String value;

    Country(final String value) {
        this.value = value;
    }

    public String getValue() {
        return value;
    }

    @Override
    public String toString() {
        return this.getValue();
    }
}

You could also add a static method to retrieve all the fields, to print them all, etc. Simply call getValue to obtain the string associated to each Enum item

mode1.name() or String.valueOf(mode1). It doesn't get better than that, I'm afraid

public enum Modes {
  MODE1("Mode1"),
  MODE2("Mode2"),
  MODE3("Mode3");

 private String value;
 public String getValue() {
    return value;
   }
 private Modes(String value) {
  this.value = value;
 } 
}

you can make a call like below wherever you want to get the value as a string from the enum.

Modes.MODE1.getvalue();

This will return "Mode1" as a String.

For my enums I don't really like to think of them being allocated with 1 String each. This is how I implement a toString() method on enums.

enum Animal
{
    DOG, CAT, BIRD;
    public String toString(){
        switch (this) {
            case DOG: return "Dog";
            case CAT: return "Cat";
            case BIRD: return "Bird";
        }
        return null;
    }
}

You can use Mode.mode1.name() however you often don't need to do this.

Mode mode =
System.out.println("The mode is "+mode);

As far as I know, the only way to get the name would be

Mode.mode1.name();

If you really need it this way, however, you could do:

public enum Modes {
    mode1 ("Mode1"),
    mode2 ("Mode2"),
    mode3 ("Mode3");

    private String name;       

    private Modes(String s) {
        name = s;
    }
}

my solution for your problem!

import java.util.HashMap;
import java.util.Map;

public enum MapEnumSample {
    Mustang("One of the fastest cars in the world!"), 
    Mercedes("One of the most beautiful cars in the world!"), 
    Ferrari("Ferrari or Mercedes, which one is the best?");

    private final String description;
    private static Map<String, String> enumMap;

    private MapEnumSample(String description) {
        this.description = description;
    }

    public String getEnumValue() {
        return description;
    }

    public static String getEnumKey(String name) {
        if (enumMap == null) {
            initializeMap();
        }
        return enumMap.get(name);
    }

    private static Map<String, String> initializeMap() {
        enumMap = new HashMap<String, String>();
        for (MapEnumSample access : MapEnumSample.values()) {
            enumMap.put(access.getEnumValue(), access.toString());
        }
        return enumMap;
    }

    public static void main(String[] args) {

        // getting value from Description
        System.out.println(MapEnumSample.getEnumKey("One of the fastest cars in the world!"));

        // getting value from Constant
        System.out.println(MapEnumSample.Mustang.getEnumValue());

        System.out.println(MapEnumSample.getEnumKey("One of the most beautiful cars in the world!"));
        System.out.println(MapEnumSample.Mercedes.getEnumValue());

        // doesnt exist in Enum
        System.out.println("Mustang or Mercedes, which one is the best?");
        System.out.println(MapEnumSample.getEnumKey("Mustang or Mercedes, which one is the best?") == null ? "I don't know!" : "I believe that "
                + MapEnumSample.getEnumKey("Ferrari or Mustang, which one is the best?") + " is the best!.");

        // exists in Enum
        System.out.println("Ferrari or Mercedes, wich one is the best?");
        System.out.println(MapEnumSample.getEnumKey("Ferrari or Mercedes, which one is the best?") == null ? "I don't know!" : "I believe that "
                + MapEnumSample.getEnumKey("Ferrari or Mercedes, which one is the best?") + " is the best!");

    }
}

You can simply use:

""+ Modes.mode1

public enum Environment
{
    PROD("https://prod.domain.com:1088/"),
    SIT("https://sit.domain.com:2019/"),
    CIT("https://cit.domain.com:8080/"),
    DEV("https://dev.domain.com:21323/");

    private String url;

    Environment(String envUrl) {
        this.url = envUrl;
    }

    public String getUrl() {
        return url;
    }
}

String prodUrl = Environment.PROD.getUrl();

It will print:

https://prod.domain.com:1088/

This design for enum string constants works in most of the cases.

Enum is just a little bit special class. Enums can store additional fields, implement methods etc. For example

public enum Modes {
    mode1('a'),
    mode2('b'),
    mode3('c'),
    ;
    char c;

    private Modes(char c) {
        this.c = c;
    }
    public char character() {
        return c;
    }
}

Now you can say:

System.out.println(Modes.mode1.character())

and see output: a

package com.common.test;

public  enum Days {


    monday(1,"Monday"),tuesday(2,"Tuesday"),wednesday(3,"Wednesday"),
    thrusday(4,"Thrusday"),friday(5,"Friday"),saturday(6,"Saturday"),sunday(7,"Sunday");

    private int id;
    private String desc;


    Days(int id,String desc){
        this.id=id;
        this.desc=desc;
    }

    public static String getDay(int id){

        for (Days day : Days.values()) {
            if (day.getId() == id) {
                return day.getDesc();
            }
        }
        return null;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getDesc() {
        return desc;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }



};

This method should work with any enum:

public enum MyEnum {
    VALUE1,
    VALUE2,
    VALUE3;

    public int getValue() {
        return this.ordinal();
    }

    public static DataType forValue(int value) {
        return values()[value];
    }

    public String toString() {
        return forValue(getValue()).name();
    }
}

i found this one is more easy for preventing type error:

public enum Modes {
    some-really-long-string,
    mode1,
    mode2,
    mode3;

    String str;

    Modes(){
        this.str = super.name();
    }

    @Override
    @NonNull
    public String toString() {
        return str;
    }

however - this may work when you need to use a String on a log/println or whenever java compiles the toString() method automatically, but on a code line like this ->

// sample method that require (string,value)
intent.putExtra(Modes.mode1 ,shareElement.getMode()); // java error
// first argument enum does not return value

instead as mentioned above you will still have to extend the enum and use .name() in those cases like this:

intent.putExtra(Modes.mode1.name() ,shareElement.getMode()); 

after many tries I have come with this solution

public static enum Operation {

    Addition, Subtraction, Multiplication, Division,;

    public String getUserFriendlyString() {
        if (this==Addition) {
            return " + ";
        } else if (this==Subtraction) {
            return " - ";
        } else if (this==Multiplication) {
            return " * ";
        } else if (this==Division) {
            return " / ";
        }
        return "undefined";
       }
}

You can try this:

public enum Modes {
    some-really-long-string,
    mode1,
    mode2,
    mode3;

    public String toString(){
        switch(this) {
            case some-really-long-string:
                return "some-really-long-string";
            case mode2:
                return "mode2";
            default: return "undefined";
        }
    }

}

use mode1.name() or String.valueOf(Modes.mode1)