Using enum as key for map [closed]

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I want to use enum as keys and a object as value. Here is the sample code snippet:

public class DistributorAuditSection implements Comparable<DistributorAuditSection>{      

     private Map questionComponentsMap;  

     public Map getQuestionComponentsMap(){  
         return questionComponentsMap;  
     }  

     public void setQuestionComponentsMap(Integer key, Object questionComponents){  
         if((questionComponentsMap == null)  || (questionComponentsMap != null && questionComponentsMap.isEmpty())){ 
             this.questionComponentsMap = new HashMap<Integer,Object>();  
         }  
         this.questionComponentsMap.put(key,questionComponents);  
     }
}

It is now a normal hashmap with integer keys and and object as values. Now I want to change it to Enummap. So that I can use the enum keys. I also don't know how to retrieve the value using Enummap.

What have you tried? What happens when you use EnumMap? To get help you need to be more specific and show you've done your homework. — Sean Owen
– Sean Owen, Commented Oct 1, 2012 at 8:06

Nicolas Filotto · Accepted Answer · 2018-09-06 12:22:44Z

53

It the same principle as Map Just Declare enum and use it as Key to EnumMap.

public enum Color {
    RED, YELLOW, GREEN
}

Map<Color, String> enumMap = new EnumMap<Color, String>(Color.class);
enumMap.put(Color.RED, "red");
String value = enumMap.get(Color.RED);

You can find more about Enums here

edited Sep 6, 2018 at 12:22

Nicolas Filotto

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answered Oct 1, 2012 at 8:10

Amit Deshpande

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2 Comments

Ross Youngblood Over a year ago

Thx. I was missing the Colors.RED concept for declaring a constant: i.e. private static final Colors R = Colors.RED;

Keshav Over a year ago

why we have added Color.class in map argument ??

Puce · Accepted Answer · 2012-10-01 08:13:07Z

9

Just replace new HashMap<Integer, Object>() with new EnumMap<MyEnum, Object>(MyEnum.class).

answered Oct 1, 2012 at 8:13

Puce

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2 Comments

user1568579 Over a year ago

public void setQuestionComponentsMap(Integer key, Object questionComponents){ what can i pass in the place of "Integer key"?coz now i am retrving enum keys.

Puce Over a year ago

If you can change the signature of that method then just replace the Integer argument with your Enum type...

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