Can a HashMap key be mutable?

Both hashcode and equals method are used in put and get method of HashMap. You need to make sure you can always get the value object from the map after you put it with the key object. No matter you change the key object or not. But Immutable object is good enough to achieve that .26 Kas 2013

The answer is NO . Making keys in any hashing data structure will cause memory leak. If we make the keys mutable then the hashcode() of the key will no more be consistent over time which will cause lookup failure for that object from the data structure.3 Ağu 2019

Make HashMap key object immutable Immutability allows you to get same hash code every time, for a key object . So it actually solves most of the problems in one go. Also, this class must honor the hashCode() and equals() methods contract.25 Oca 2022

We used to use the unmodifiableMap() method of Collections class to create unmodifiable(immutable) Map. Map<String,String> map = new HashMap<String, String>(); Map<String,String> immutableMap = Collections. unmodifiableMap(map);