BoxStoreBuilder: do not leak Store when setting as default fails

Author: greenrobot-team

CHANGELOG.md

@@ -9,6 +9,7 @@ For more insights into what changed in the ObjectBox C++ core, [check the Object
 - When re-creating a `BoxStore` for the same directory and `close()` wasn't called on the previous instance, don't throw
   an "Another BoxStore is still open for this directory" exception. Note that calling `close()` *is recommended* before 
   creating a new instance. [#1201](https://github.com/objectbox/objectbox-java/issues/1201)
+- When using `BoxStoreBuilder.buildDefault()`, don't leak Store when setting as default fails.
 
 ## 4.3.1 - 2025-08-12
 

objectbox-java/src/main/java/io/objectbox/BoxStoreBuilder.java

@@ -679,7 +679,13 @@ static File getDbDir(@Nullable File baseDirectoryOrNull, @Nullable String nameOr
      */
     public BoxStore buildDefault() {
         BoxStore store = build();
-        BoxStore.setDefault(store);
+        try {
+            BoxStore.setDefault(store);
+        } catch (IllegalStateException e) {
+            // Clean up the new store if it can't be set as default
+            store.close();
+            throw e;
+        }
         return store;
     }