diff --git a/src/main/java/de/deadlocker8/budgetmaster/database/BackupItemParser.java b/src/main/java/de/deadlocker8/budgetmaster/database/BackupItemParser.java
index c189b88acc881055e461f6560b84123036ded37a..bda62e21f9eee1b06b46108db226a1adff0d8b86 100644
--- a/src/main/java/de/deadlocker8/budgetmaster/database/BackupItemParser.java
+++ b/src/main/java/de/deadlocker8/budgetmaster/database/BackupItemParser.java
@@ -9,6 +9,10 @@ import java.util.List;
 
 public class BackupItemParser
 {
+	private BackupItemParser()
+	{
+	}
+
 	public static <T> List<T> parseItems(JsonArray jsonArray, Class<T> itemType)
 	{
 		List<T> parsedItems = new ArrayList<>();
diff --git a/src/main/java/de/deadlocker8/budgetmaster/database/DatabaseParser.java b/src/main/java/de/deadlocker8/budgetmaster/database/DatabaseParser.java
index c8da102b5278216dad10af71f35deb36980348b4..d47a4260bf07b41f1e3cd2cd3f6e60a856c16407 100644
--- a/src/main/java/de/deadlocker8/budgetmaster/database/DatabaseParser.java
+++ b/src/main/java/de/deadlocker8/budgetmaster/database/DatabaseParser.java
@@ -15,8 +15,8 @@ public class DatabaseParser
 {
 	final Logger LOGGER = LoggerFactory.getLogger(this.getClass());
 
-	private final int MINIMUM_VERSION = 4;
-	private final int LATEST_VERSION = 5;
+	private static final int MINIMUM_VERSION = 4;
+	private static final int LATEST_VERSION = 5;
 
 	private final String jsonString;
 
diff --git a/src/main/java/de/deadlocker8/budgetmaster/database/model/v4/BackupRepeatingEndOption_v4.java b/src/main/java/de/deadlocker8/budgetmaster/database/model/v4/BackupRepeatingEndOption_v4.java
index a12f213e80ce509639687ad2bd7e8206a7d0876e..2c9dfc5f993805b5d725340946071f2d71316d55 100644
--- a/src/main/java/de/deadlocker8/budgetmaster/database/model/v4/BackupRepeatingEndOption_v4.java
+++ b/src/main/java/de/deadlocker8/budgetmaster/database/model/v4/BackupRepeatingEndOption_v4.java
@@ -10,6 +10,7 @@ public class BackupRepeatingEndOption_v4
 
 	public BackupRepeatingEndOption_v4()
 	{
+		// for GSON
 	}
 
 	public String getLocalizationKey()
diff --git a/src/main/java/de/deadlocker8/budgetmaster/database/model/v4/BackupTemplate_v4.java b/src/main/java/de/deadlocker8/budgetmaster/database/model/v4/BackupTemplate_v4.java
index e7d351cfc9a0377473197aa11d280879a0a984f8..3c3f29701e813d60f17d7e2b282e60836a7e12da 100644
--- a/src/main/java/de/deadlocker8/budgetmaster/database/model/v4/BackupTemplate_v4.java
+++ b/src/main/java/de/deadlocker8/budgetmaster/database/model/v4/BackupTemplate_v4.java
@@ -23,6 +23,7 @@ public class BackupTemplate_v4 implements BackupTransactionBase_v4, Upgradeable<
 
 	public BackupTemplate_v4()
 	{
+		// for GSON
 	}
 
 	public String getTemplateName()
diff --git a/src/main/java/de/deadlocker8/budgetmaster/database/model/v4/BackupTransaction_v4.java b/src/main/java/de/deadlocker8/budgetmaster/database/model/v4/BackupTransaction_v4.java
index efbca7711a65382b13fde6d58c3d99207b693c83..265ed8999fe215e09d22f82075a7428e325e9a49 100644
--- a/src/main/java/de/deadlocker8/budgetmaster/database/model/v4/BackupTransaction_v4.java
+++ b/src/main/java/de/deadlocker8/budgetmaster/database/model/v4/BackupTransaction_v4.java
@@ -24,6 +24,7 @@ public class BackupTransaction_v4 implements BackupTransactionBase_v4, Upgradeab
 
 	public BackupTransaction_v4()
 	{
+		// for GSON
 	}
 
 	public Integer getAmount()
diff --git a/src/main/java/de/deadlocker8/budgetmaster/database/model/v5/BackupTransaction_v5.java b/src/main/java/de/deadlocker8/budgetmaster/database/model/v5/BackupTransaction_v5.java
index 8a79264d84f84382244b753db5c8dbb3411a9cb4..299d521c1021003e995c85ae8779d5d3b1f08419 100644
--- a/src/main/java/de/deadlocker8/budgetmaster/database/model/v5/BackupTransaction_v5.java
+++ b/src/main/java/de/deadlocker8/budgetmaster/database/model/v5/BackupTransaction_v5.java
@@ -21,6 +21,7 @@ public class BackupTransaction_v5
 
 	public BackupTransaction_v5()
 	{
+		// for GSON
 	}
 
 	public BackupTransaction_v5(Integer amount, Boolean isExpenditure, String date, BackupAccount_v5 account, BackupCategory_v5 category, String name, String description, List<Tag> tags, BackupRepeatingOption_v4 repeatingOption, BackupAccount_v5 transferAccount)