Can a map assign the same value to two different keys?

Can a map assign the same value to two different keys?

HashMap doesn’t allow duplicate keys but allows duplicate values. That means A single key can’t contain more than 1 value but more than 1 key can contain a single value. HashMap allows null key also but only once and multiple null values.

Can a HashMap have two keys?

You can’t have an hash map with multiple keys, but you can have an object that takes multiple parameters as the key.

What will happen if two different keys of HashMap return the same hashCode ()?

If two keys are different, then it doesn’t matter if their hash codes are the same or not. They will be stored in the same bucket if their hash codes are the same, and in this case, the hashmap will use equals() to tell them apart.

Is key unique in HashMap?

HashMap is a collection to store (key,value) pairs and According to the documentation of HashMap the keys are always unique. If you add a key which already exists(collision) in the hashmap, the old value will be replaced.

Can a map key have multiple values C++?

Multimap is similar to map with an addition that multiple elements can have same keys. Also, it is NOT required that the key value and mapped value pair has to be unique in this case.

What happens when two objects have same Hashcode?

If two objects have the same hash code, it doesn’t mean that they are equal. Overriding equals() alone will make your business fail with hashing data structures like: HashSet, HashMap, HashTable etc. Overriding hashcode() alone doesn’t force Java to ignore memory addresses when comparing two objects.

What happens if Hashcode returns same value?

When two key return same hashcode, they end up in the same bucket. Now, in order to find the correct value, you used keys. equals() method to compare with key stored in each Entry of linked list there. equals() method, because that’s what interviewer is looking for.

How do I put multiple values in a HashMap?

How to add multiple values per key to a Java HashMap

1. Stick with the standard APIs and add a collection class like a ‘Vector’ or ‘ArrayList’ to your map or set.
2. Use the MultiMap and MultiValueMap classes from the Apache Commons library.

Can a map key have multiple values?

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 a hashmap have multiple values under the same key?

Take a look at Multimap from the guava-libraries and its implementation – HashMultimap A collection similar to a Map, but which may associate multiple values with a single 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.

Do you need a hashmap for a collection of values?

No, not just as a HashMap. You’d basically need a HashMap from a key to a collection of values. If you’re happy to use external libraries, Guava has exactly this concept in Multimap with implementations such as ArrayListMultimap, HashMultimap, LinkedHashMultimap etc.

Which is better an array or a hashmap?

A hashmap is a structure that is optimized for associative access of the values using the keys, but is in no way better in doing the reverse then an array for instance. I don’t think you can do any better then just iterate.

How to map multiple values under the 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. I use Map for associating multiple values with a key in a Map.