Which map can have duplicate keys?
Duplicate keys are not allowed in a Map….Difference between HashMap and HashSet.
| Basic | HashSet | HashMap |
|---|---|---|
| Implements | Set interface | Map interface |
| Duplicates | No | Yes duplicates values are allowed but no duplicate key is allowed |
| Dummy values | Yes | No |
Can a map contains duplicate keys?
A Map is an object that maps keys to values. A map cannot contain duplicate keys: Each key can map to at most one value.
Can map store duplicate values?
Map does not supports duplicate keys. you can use collection as value against same key. Because if the map previously contained a mapping for the key, the old value is replaced by the specified value.
Which map contains duplicate keys in Java?
You can use a TreeMap with a custom Comparator in order to treat each key as unequal to the others. It would also preserve the insertion order in your map, just like a LinkedHashMap. So, the net result would be like a LinkedHashMap which allows duplicate keys!
Does TreeMap allow duplicate values?
A TreeMap cannot contain duplicate keys. TreeMap cannot contain the null key. However, It can have null values.
Does HashMap allow duplicate values?
HashMap does not allow duplicate keys however it allows to have duplicate values. HashSet permits to have a single null value. HashMap permits single null key and any number of null values.
Can HashMap have duplicate values?
HashMap does not allow duplicate keys however it allows to have duplicate values. HashSet permits to have a single null value.
Can a HashMap have multiple values for same key?
HashMap can be used to store key-value pairs. But sometimes you may want to store multiple values for the same key. For example: For Key A, you want to store – Apple, Aeroplane.
Can HashMap hold duplicate keys?
Does Hashtable allow duplicate keys?
Hashtable Features It does not accept duplicate keys. It stores key-value pairs in hash table data structure which internally maintains an array of list. Each list may be referred as a bucket. In case of collisions, pairs are stored in this list.
Can LinkedHashMap have duplicate keys?
A LinkedHashMap cannot contain duplicate keys. LinkedHashMap can have null values and the null key. Unlike HashMap, the iteration order of the elements in a LinkedHashMap is predictable.
What will happen if we insert duplicate key in Map?
If you try to insert the duplicate key, it will replace the element of the corresponding key. HashMap is similar to HashTable, but it is unsynchronized. It allows to store the null keys as well, but there should be only one null key object and there can be any number of null values.