EnuMap in Java

EnumMap is a specialized Map implementation in Java that is designed to be used with enum keys. It provides a very efficient and type-safe way to store and manipulate enum-based data. EnumMap is a final class that implements the Map interface and is part of the Java Collections Framework.

Here is an example of how to create an EnumMap in Java:

enum Color {
    RED, GREEN, BLUE
}

EnumMap<Color, Integer> enumMap = new EnumMap<>(Color.class);
enumMap.put(Color.RED, 1);
enumMap.put(Color.GREEN, 2);
enumMap.put(Color.BLUE, 3);

In this example, a new EnumMap is created with keys of type Color and values of type Integer. The put method is used to add entries to the map.

EnumMap provides several methods to access and modify the entries in the map. Some of the most commonly used methods are:

1. put(K key, V value): This method is used to add a new entry to the map with the specified key and value.

enumMap.put(Color.RED, 4);

2. get(Object key): This method is used to get the value associated with the specified key in the map.

Integer value = enumMap.get(Color.GREEN);

3. remove(Object key): This method is used to remove the entry with the specified key from the map.

enumMap.remove(Color.BLUE);

4. clear(): This method is used to remove all entries from the map.

enumMap.clear();

5. keySet(): This method returns a set of all the keys in the map.

Set<Color> keys = enumMap.keySet();

6. values(): This method returns a collection of all the values in the map.

Collection<Integer> values = enumMap.values();

7. entrySet(): This method returns a set of all the entries in the map.

Set<Map.Entry<Color, Integer>> entries = enumMap.entrySet();

One of the main advantages of using an EnumMap is that it provides very high performance and type safety. Since enum values are unique and fixed, an EnumMap can be implemented as a compact array, making it very fast and efficient. Additionally, the type safety of the map ensures that only the correct enum values can be used as keys.

Overall, EnumMap is a very efficient and type-safe way to store and manipulate enum-based data in Java.