add PropertyQuery.count()

Author: greenrobot

objectbox-java/src/main/java/io/objectbox/query/PropertyQuery.java

@@ -94,6 +94,8 @@ native String nativeFindString(long handle, long cursorHandle, int propertyId, b
 
     native double nativeAvg(long handle, long cursorHandle, int propertyId);
 
+    native long nativeCount(long handle, long cursorHandle, int propertyId, boolean distinct);
+
     /** Clears all values (e.g. distinct and null value). */
     public PropertyQuery reset() {
         distinct = false;
@@ -450,4 +452,13 @@ public Double call() {
         });
     }
 
-}
+    public long count() {
+        return (Long) query.callInReadTx(new Callable<Long>() {
+            @Override
+            public Long call() {
+                return nativeCount(queryHandle, query.cursorHandle(), propertyId, distinct);
+            }
+        });
+    }
+
+}

tests/objectbox-java-test/src/test/java/io/objectbox/query/PropertyQueryTest.java

@@ -427,6 +427,19 @@ public void testFindShorts_wrongPropertyType() {
         box.query().build().property(simpleInt).findShorts();
     }
 
+    @Test
+    public void testCount() {
+        putTestEntity(null, 1000);
+        putTestEntity("BAR", 100);
+        putTestEntitiesStrings();
+        putTestEntity("banana", 101);
+        Query<TestEntity> query = box.query().build();
+        PropertyQuery stringQuery = query.property(simpleString);
+        assertEquals(8, query.count());
+        assertEquals(7, stringQuery.count());
+        assertEquals(6, stringQuery.distinct().count());
+    }
+
     private List<TestEntity> putTestEntitiesScalars() {
         return putTestEntities(10, null, 2000);
     }