How can issues with data modification inside a hash table be avoided?

Problems with changing data inside a hash table (e.g., HashMap in Java) occur if the object used as a key is modified so that its hash code or equality changes after being placed in the table. This makes the element inaccessible for search.

To avoid such issues:

• Use immutable objects as keys (e.g., strings, wrappers over primitives).
• If mutable objects are used, do not change fields involved in hashCode() and equals() after inserting into the hash table.
• If you need to change the key, first remove the element from the table, modify the key, then add it back.

Example:

Map<MyKey, String> map = new HashMap<>();
MyKey key = new MyKey("initial");
map.put(key, "value");

// Do not change fields affecting hashCode/equals
// otherwise map.get(key) may return null

Thus, keys should be stable for correct hash table operation.