- The reason that HashMap is faster than HashSet is that the HashMap uses the unique keys to access the values
- It stores each value with a corresponding key and we can retrieve these values faster using keys during iteration
- While HashSet is completely based on objects and therefore retrieval of values is slower
Then, Can a HashMap have multiple values for same key? The Map interface stores the elements as key-value pairs It does not allow duplicate keys but allows duplicate values HashMap and LinkedHashMap classes are the widely used implementations of the Map interface But the limitation of the Map interface is that multiple values cannot be stored against a single key
Can HashSet have null key?
Null values in HashSet − The HashSet object allows null values but, you can add only one null element to it Though you add more null values if you try to print its contents, it displays only one null
furthermore, Does HashMap allow null key? HashMap allows one null key and multiple null values whereas Hashtable doesn’t allow any null key or value HashMap is generally preferred over HashTable if thread synchronization is not needed
Does HashSet remove duplicates? Set implementations in Java has only unique elements Therefore, it can be used to remove duplicate elements
How HashMap store duplicate values?
Map<String, List<String>> map = new HashMap<>(); List<String> list = new ArrayList<>(); map put(“key1”, list); map get(“key1”) add(“value1”); map
How HashMap store different values with same key?
If you call put(K, V) twice, with the same key but different values, the multimap contains mappings from the key to both values Show activity on this post I use Map<KeyType, Object> for associating multiple values with a key in a Map This way, I can store multiple values of different types associated with a key
How HashMap prevents duplicate values in Java?
- Take a hash map, which will store all the elements which have appeared before
- Traverse the array
- Check if the element is present in the hash map
- If yes, continue traversing the array
- Else Print the element
Why HashMap is faster than Hashtable?
HashMap is faster than Hashtable due to the fact that Hashtable implicitly checks for synchronization on each method call even in a single thread environment HashMap allows storing null values, while Hashtable doesn’t HashMap can be iterated by an Iterator which is considered as fail-fast
Can HashMap have NULL values?
HashMap allows one null key and multiple null values whereas Hashtable doesn’t allow any null key or value
Why null key is allowed in HashMap?
How is it useful to have such a key and values in HashMap? It is useful to explicitly store null to distinguish between a key that you know exists but doesn’t have an associated value and a key that doesn’t exist An example is a list of registered users and their birthdays
Why is HashMap not thread-safe?
It fails because it times out when the threads go into an infinite loop because of memory corruption of HashMap However, it may not fail for you depending on number of cores and other architecture details