What is the EnumMap.remove(key) method in Java?

EnumMap is similar to Map, except that EnumMap only takes the Enum type as a key. Also, all the keys must be from a single Enum type. For further details, refer here.

In EnumMap, we can use the remove method to remove the mapping of the specified key.

Syntax

public V remove(Object key)

Parameters

The key whose mapping is to be removed is passed as an argument.

Return value

If there is a mapping present for the specified key, then the mapping is removed and the removed value is returned.
If there is no mapping present for the specified key, then null is returned.

Code

The code snippet below shows how to use the remove method.

import java.util.EnumMap;
class Remove {
    enum Days{
      MON, TUE, WED, THUR, FRI, SAT, SUN 
    };
    public static void main( String args[] ) {
        EnumMap<Days, String> map = new EnumMap<>(Days.class);
        map.put(Days.MON, "chest");
        map.put(Days.TUE, "leg");
        String returnValue = map.remove(Days.MON);
        System.out.println("\nThe return value for map.remove(Days.MON) - " + returnValue);
        System.out.println("The map is -" + map );
        
        returnValue = map.remove(Days.WED);
        System.out.println("\nThe return value for map.remove(Days.WED) - " + returnValue);
        System.out.println("The map is -" + map );
    }
}

Explanation

In the code snippet above:

In line 1, we import the EnumMap class.
In line 3, we create an enum for days of the week with the name Days.
In line 7, we create an EnumMap object with the name map.
In line 8 and 9, we use the put method to add two mappings {Days.MON="chest", Days.TUE="leg"} to the map object.
In line 11, we use the remove method to remove the mapping for the key Days.MON. There is a mapping for the key Days.MON, so it will be removed and the value chest mapped to that will be returned.
In line 14, we use the remove method to remove the mapping for the key Days.WED. There is no such entry present, so null will be returned.

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