Difference Between Map And HashMap In Java

Java

5 MIN READ

September 8, 2021

Difference Between Map And HashMap In Java

Map and HashMap – These two terms have been contrasted in this post. Let’s take a closer look at them.

HashMap is a non-synchronized class of the Java Collection Framework that contains null values and keys, whereas Map is a Java interface, which is used to map key-pair values. Although a key->value map and a method to iterate over the keys are usually the quality that both have but timing guarantees and key order are the most important differences between these two classes (Map and HashMap).

How Map Is Different From HashMap In Java?

HashMap does not maintain any insertion order of its elements hence it is quicker than Map.
In contrast to Map, HashMap can hold duplicate values.
It’s possible to implement the Map interface by utilizing its implementing classes. Hashmap is all about implementing the Map Interface.
The map does not allow storage of a single null key whereas HashMap can store multiple null values along with a single null key.
Unlike Map which is an interface, HashMap is a non-synchronized class of the Java Collections framework.
HashMap and TreeMap are two implementations of Map whereas the HashMap class uses Map interface.

Methods in HashMap

Note: K stands for the kind of keys in the map, and V stands for the type of values mapped in the map.

computeIfAbsent(K key, Function<? super K,? extends V> mappingFunction) – Calculates the value of the provided key using the given mapping function and enters it into this map if it has not been previously associated with a value.

Clear() – Eliminates each mapping from this map.

containsValue(Object value) – The method for determining whether or not this map maps one or more keys to the provided value.

compute(K key, BiFunction<? super K, ? super V,? extends V> remappingFunction) –< Calculates the mapping between the requested key and its current mapped value or with null if no current mapping exists.

Clone() – Creates a shallow clone of this HashMap object, retaining the keys and values.

computeIfPresent(K key, BiFunction<? super K, ? super V,? extends V> remappingFunction) – Calculates a new mapping if the specified key exists and its current mapped value is given.

containsKey(Object key) – The technique for determining whether or not this map has a mapping for the provided key.

entrySet() – Used to construct a set of identical elements contained in a HashMap

get(Object key) – The method has its own properties to returns the value to which the provided key is mapped or to null.

hashMap.values() – utilized to construct a collection out of the values of the map.

Methods in Map Interface

get(Object) – This function is used to get the value mapped to a certain key specified in the input.

hashCode() – This method returns the hash code of a string containing the key and value for the given map.

equals(Object) – This approach is used to determine how similar two maps are. It checks if the elements of one map provided as a parameter are the same as the elements of this map.

put(Object, Object) – This method is used to link the provided value to the specified key.

putAll(Map) – All of the mappings from the supplied map are copied to this map using this technique.

isEmpty() – Determines whether the specified string is empty.

size() – The number of key/value pairs accessible in the map is returned by this method.

values() – This technique is used to construct a collection from the map’s values. It essentially returns a Collection view of the HashMap’s values.

keySet() – Using this approach, you may get a Set view of the keys in this map, thus any changes to the map get automatically reflected in this set and vice versa.

clear() – Use this function to clear and delete all elements or mappings from a given map collection.

containsKey(Object) – The primary goal of this function is to determine whether a given key is mapped in the Map. Here the key is used as a parameter. And it returns True if the key element is mapped in the map.

containsValue(Object) – This method determines if a given value in the Map is mapped by a single key or many keys. Here the value is used as a parameter and returns True if the key element is mapped in the map.

entrySet() – This method is used to produce a set from the elements of the map. We can either return a set view of the map, or we can create a new set and store the map parts in it.

remove(Object) – If the mapping for a key is existing in the map, this technique is used to delete it.

In a Nutshell,

HashMap and Map both are similar in one way or two but the difference lies in the interface. For example, HashMap<String, Object> is the interface in the case of HashMap, whereas, in Map, it’s Map<String, Object. HashMap is a dynamic form of Map, whereas Map is a static type of Map. This implies that the compiler will treat your Map object as if it were of type Map, even though it may point to any of its subtypes at runtime. Besides that, there’s a common denominator. Furthermore, you can also update the Map object without violating your contract with any code that is utilizing it, which is an advantage of using Map<String, Object>. But if you declare it as HashMap<String, Object> and want to change the underlying implementation, there will be a need for a contract modification.

Programming against interfaces rather than implementations has the extra benefit of maintaining flexibility: for example, you may modify the dynamic type of Map at runtime as long as it’s a subtype of Map, and change the map’s behavior on the fly. There are many more differences between Map and HashMap in Java, and you may contact our Ksolves experts at any moment to learn more. We specialize in Java programming and are experts in java/j2ee development using jquery.

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