What reasons can lead to data loss inside a HashMap structure?

Data loss inside a HashMap structure in Android (or in Java/Kotlin) can occur for several reasons:

• Hash collisions: If the hash function poorly distributes keys, multiple keys may end up in the same bucket, slowing down operations and potentially causing errors if implemented incorrectly.
• Changing keys after insertion: If the object used as a key is modified after being placed in the HashMap (for example, if fields involved in calculating hashCode or equals are changed), searching for such a key may fail, which appears as data loss.
• Concurrent access without synchronization: When accessed simultaneously from multiple threads without proper synchronization, HashMap can become corrupted, leading to data loss or corruption.
• Resizing and rehashing: When the number of elements grows, HashMap automatically expands and redistributes elements. If an error occurs during this process or if hashCode/equals methods are overridden incorrectly, data can be lost.

It is important to use immutable keys and, if necessary, employ thread-safe structures (such as ConcurrentHashMap).