Styjun

Question

• I would like a list of key value pair such as a HashMap for instance or other if recommended.




• This list should contains unique keys objects used to retrieve the values.




• Keys should NOT be a STRING, since string is not unique and any value can be passed.




• Also constants are limited and are using the concepts of strings as well and should not be considered.

Example

• What is wanted is for instance list[Color.Red] = "Red".




• At this stage, i have created an enum containing all the keys.
  For instance enum ColorRED,BLUE then add it to a new HashMap.




• So the only way to retrieve a color, is to use the enum as a key list[Color.RED].

Implementation

public final static Map<Color, String> colors = new HashMap<>();
public final static enum ColorRED, BLUE;
static

 colors.put(RED, "red");
 colors.put(BLUE, "blue");

public static string getColor(Color color)

 return colors.get(color);

Need Help

Is there a type of Collection in Java that could do the job ?
If not then what might be the best practice to do so ?

The keys are unique in all maps. Add duplicate key, then it will be overwritten.. The difference between the various maps implementations concern the possibility of null keys, the order of iteration and concurrency issues.

exemple:

Map hm = new HashMap();
hm.put("1", new Integer(1));
hm.put("2", new Integer(2));
hm.put("3", new Integer(3));
hm.put("4", new Integer(4));
hm.put("1", new Integer(5));// value integer 1 is overwritten by 5

In addition, Map key are generic, you can put what you want, not only String, exemple:

Map<Integer, String> hm = new HashMap<>();
hm.put(10, "1");

Potential Solution

After checking around enum and its possibilities, there is a way to assign values to a Key in an enum, like follow.

• Create a new enum and assign Key such as public enum ColorRED;.


• Add a constructor parameter to it such as public enum ColorRED("red");


• Add a constructor to the enum such as public enum ColorRED("red"); Color()


• Add a new field inside enum called value such as private String value; public String getValue() return value;


• Set field value in constructor of enum such as Color(String value) this.value = value;


• Enum work in that way, for each Key you add it creates a new instance field String value linked to the Key, then it will use the constructor you have declared to save the value.

Full Implementation

public enum Color

 //[PROP]
 RED("red"),
 GREEN("green"),
 BLUE("blue");

 private String value;
 public String getValue return value;

 //[BUILD]
 Color(String value) this.value = value;

 //[UTIL]
 Color[] getKeys() return this.values; //values method is already a method existing in enum class, we are just proposing another method name here as a facade for simplicity.

• If we want to retrieve an item we just simply do Color.RED.value, in this way only existing keys returned wanted value.


• Note that value doesn't needs to be the name of the key but could be a totally different value.

Please comment if you have any simpler solution without putting more complexity to the solution.