Add a changelog

Author: greenrobot-team

CHANGELOG.md

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+# Changelog
+
+Notable changes to the ObjectBox Java library.
+
+For more insights into what changed in the ObjectBox C++ core, [check the ObjectBox C changelog](https://github.com/objectbox/objectbox-c/blob/main/CHANGELOG.md).
+
+## 4.0.2 - 2024-08-20
+
+* Add convenience `oneOf` and `notOneOf` conditions that accept `Date` to avoid manual conversion using `getTime()`.
+* When `BoxStore` is closing, briefly wait on active transactions to finish.
+* Guard against crashes when `BoxStore` was closed, but database operations do still occur concurrently (transactions are still active).
+
+## 4.0.1 - 2024-06-03
+
+* Examples: added [Vector Search example](https://github.com/objectbox/objectbox-examples/tree/main/java-main-vector-search) that demonstrates how to perform on-device [approximate nearest neighbor (ANN) search](https://docs.objectbox.io/on-device-vector-search).
+* Revert deprecation of `Box.query()`, it is still useful for queries without any condition.
+* Add note on old query API methods of `QueryBuilder` that they are not recommended for new projects. Use [the new query APIs](https://docs.objectbox.io/queries) instead.
+* Update and expand documentation on `ToOne` and `ToMany`.
+
+## 4.0.0 - Vector Search - 2024-05-16
+
+**ObjectBox now supports** [**Vector Search**](https://docs.objectbox.io/ann-vector-search) to enable efficient similarity searches.
+
+This is particularly useful for AI/ML/RAG applications, e.g. image, audio, or text similarity. Other use cases include semantic search or recommendation engines.
+
+Create a Vector (HNSW) index for a floating point vector property. For example, a `City` with a location vector:
+
+```java
+@Entity
+public class City {
+
+    @HnswIndex(dimensions = 2)
+    float[] location;
+    
+}
+```
+
+Perform a nearest neighbor search using the new `nearestNeighbors(queryVector, maxResultCount)` query condition and the new "find with scores" query methods (the score is the distance to the query vector). For example, find the 2 closest cities:
+
+```java
+final float[] madrid = {40.416775F, -3.703790F};
+final Query<City> query = box
+        .query(City_.location.nearestNeighbors(madrid, 2))
+        .build();
+final City closest = query.findWithScores().get(0).get();
+```
+
+For an introduction to Vector Search, more details and other supported languages see the [Vector Search documentation](https://docs.objectbox.io/ann-vector-search).
+
+* BoxStore: deprecated `BoxStore.sizeOnDisk()`. Instead use one of the new APIs to determine the size of a database:
+  * `BoxStore.getDbSize()` which for a file-based database returns the file size and for an in-memory database returns the approximately used memory,
+  * `BoxStore.getDbSizeOnDisk()` which only returns a non-zero size for a file-based database.
+* Query: add properly named `setParameter(prop, value)` methods that only accept a single parameter value, deprecated the old `setParameters(prop, value)` variants.
+* Sync: add `SyncCredentials.userAndPassword(user, password)`.
+* Gradle plugin: the license of the [Gradle plugin](https://github.com/objectbox/objectbox-java-generator) has changed to the GNU Affero General Public License (AGPL).
+
+## Previous versions
+
+See the [Changelogs in the documentation](https://docs.objectbox.io/changelogs).