EnumMap trong Java là gì?

public class JavaEnumMap {

    enum Colour {
        RED,
        BLUE,
        BLACK,
        GREEN
    }
}

    public static void main(String[] args) {

        EnumMap<Colour, Integer> colours = new EnumMap<Colour, Integer>(Colour.class);

        colours.put(Colour.RED, 1);
        colours.put(Colour.BLUE, 2);
        colours.put(Colour.BLACK, 3);
        colours.put(Colour.GREEN, 4);
}

System.out.println("Printing all keys in the map " + colours.keySet());

Printing all keys in the map [RED, BLUE, BLACK, GREEN]

System.out.println("Printing the keys and the values in the map " + colours.entrySet());

Printing the keys and the values in the map [RED=1, BLUE=2, BLACK=3, GREEN=4]

System.out.println("Printing the values in the map " + colours.values());

Printing the values in the map [1, 2, 3, 4]

System.out.println("Retrieve the value from the enumMap " + colours.get(Colour.RED));

Retrieve the value from the enumMap: 1

System.out.println("Removing the key: " + colours.remove(Colour.GREEN));

Removing the key: 4
The enumMap now has: {RED=1, BLUE=2}

System.out.println("Removing the key and the value from the enumMap: " + colours.remove(Colour.BLACK, 3));
Removing the key and the value from the enumMap: true
The enumMap now has: {RED=1, BLUE=2}

The enumMap now has: {RED=1, BLUE=2}

colours.replace(Colour.RED, 5);

System.out.println("The new enum now has: " + colours);

The new enum now has: {RED=5, BLUE=2}

colours.replace(Colour.BLUE, 2, 4);

         System.out.println("The new enum now has: " + colours);

The new enum now has: {RED=5, BLUE=4}

      colours.replaceAll((key, oldValue) -> oldValue + 7);

        System.out.println("EnumMap using replaceAll(): " + colours);

EnumMap using replaceAll(): {RED=12, BLUE=11}