EnumMap extends AbstractMap and implements Map. It uses an enum type as keys.
The EnumMap class provides a Map implementation whose keys are the members of the same enum. Null keys are not permitted.
It is a generic class that has this declaration:
class EnumMap, V>
K specifies the type of key
V specifies the type of value.
K must extend Enum, which enforces that hat the keys must be of an enum type.
EnumMap defines the following constructors:
EnumMap(Class kType)
creates an empty EnumMap of type kType.
EnumMap(Map m)
creates an EnumMap map that contains the same entries as m.
EnumMap(EnumMap em)
creates an EnumMap initialized with the values in em.
The following code stores Size enum to a EnumMap.
import java.util.EnumMap;
public class Main {
public static void main(String[] args) {
EnumMap sizeMap = new EnumMap(Size.class);
sizeMap.put(Size.S, "S");
sizeMap.put(Size.M, "M");
sizeMap.put(Size.L, "L");
sizeMap.put(Size.XL, "XL");
sizeMap.put(Size.XXL, "XXL");
sizeMap.put(Size.XXXL, "XXXL");
for (Size size : Size.values()) {
System.out.println(size + ":" + sizeMap.get(size));
}
}
}
enum Size {
S, M, L, XL, XXL, XXXL;
}
The following code maps enum to an integer.
import java.util.EnumMap;
import java.util.Map;
enum Coin {
PENNY, NICKEL, DIME, QUARTER
}
public class Main {
public static void main(String[] args) {
Map map = new EnumMap(Coin.class);
map.put(Coin.PENNY, 1);
map.put(Coin.NICKEL, 5);
map.put(Coin.DIME, 10);
map.put(Coin.QUARTER, 25);
System.out.println(map);
Map mapCopy = new EnumMap(map);
System.out.println(mapCopy);
}
}