EnumMap class implements the Map class and enables the use of enum type keys. Enum maps are maintained in the natural order of their keys. It is important to note that null keys are not permitted. If attempt has been made for adding a null key, NullPointerException will be thrown. However, even though null keys are not allowed, null values are. Since all…
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WeakHashMap in Java implements the Map interface and represents a hash table that has weak keys. If a key is not in an ordinary use, the entry from the map will be automatically removed. This is what differentiates it from other Map implementations. Null and non-null values are supported and the performance is similar to HashMap class in and…
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IdentityHashMap implements the Map interface and two keys are considered equal when checked as k1==k2 (not by using equals method). This itself violates the Map‘s general contract, which means that IdentityHashMap is clearly not a general-purpose Map implementation. There are only so many cases where this class would be useful. IdentityHashMap permits both null values and the null key, alongside all optional map…
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SortedMap interface extends Map and ensures that all entries are in an ascending key order (hence SortedMap). If you want to have it in a descending order, you will need to override the Compare method in the SortedMap which we will do shortly. TreeMap implements SortedMap and it either orders the keys by their natural…
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Even though Map is implemented by many classes, many of them are not thread-safe or some of them are but not efficient. This is why ConcurrentMap was introduced in Java 1.5. It is thread-safe and efficient. Overridden default implementations: compute replaceAll forEach getOrDefault computerIfAbsent computerIfPresent ConcurrentMap consists of an array of nodes that are represented as table…
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