diff --git a/src/main/java/com/nextcloud/android/sso/Constants.java b/src/main/java/com/nextcloud/android/sso/Constants.java
index aa52127cfe..4fffd8ad91 100644
--- a/src/main/java/com/nextcloud/android/sso/Constants.java
+++ b/src/main/java/com/nextcloud/android/sso/Constants.java
@@ -2,6 +2,10 @@ package com.nextcloud.android.sso;
 
 public class Constants {
 
+    private Constants() {
+        // No instance
+    }
+
     // Authenticator related constants
     public static final String SSO_USERNAME = "username";
     public static final String SSO_TOKEN = "token";
diff --git a/src/main/java/com/owncloud/android/authentication/OAuth2Constants.java b/src/main/java/com/owncloud/android/authentication/OAuth2Constants.java
index f6bd664d92..45ebe1cc39 100644
--- a/src/main/java/com/owncloud/android/authentication/OAuth2Constants.java
+++ b/src/main/java/com/owncloud/android/authentication/OAuth2Constants.java
@@ -27,6 +27,10 @@ package com.owncloud.android.authentication;
  */
 
 public class OAuth2Constants {
+
+    private OAuth2Constants() {
+        // No instance
+    }
     
     /// Parameters to send to the Authorization Endpoint
     public static final String KEY_RESPONSE_TYPE = "response_type";
diff --git a/src/main/java/com/owncloud/android/db/ProviderMeta.java b/src/main/java/com/owncloud/android/db/ProviderMeta.java
index 0a5a422426..7257bfcf2b 100644
--- a/src/main/java/com/owncloud/android/db/ProviderMeta.java
+++ b/src/main/java/com/owncloud/android/db/ProviderMeta.java
@@ -35,9 +35,15 @@ public class ProviderMeta {
     public static final int DB_VERSION = 44;
 
     private ProviderMeta() {
+        // No instance
     }
 
     static public class ProviderTableMeta implements BaseColumns {
+
+        private ProviderTableMeta() {
+            // No instance
+        }
+
         public static final String FILE_TABLE_NAME = "filelist";
         public static final String OCSHARES_TABLE_NAME = "ocshares";
         public static final String CAPABILITIES_TABLE_NAME = "capabilities";
diff --git a/src/main/java/com/owncloud/android/utils/MimeType.java b/src/main/java/com/owncloud/android/utils/MimeType.java
index 50a5345910..949e4a5b80 100644
--- a/src/main/java/com/owncloud/android/utils/MimeType.java
+++ b/src/main/java/com/owncloud/android/utils/MimeType.java
@@ -21,6 +21,11 @@ package com.owncloud.android.utils;
  * Class containing the mime types.
  */
 public class MimeType {
+
+    private MimeType() {
+        // No instance
+    }
+    
     public static final String DIRECTORY = "DIR";
     public static final String JPEG = "image/jpeg";
     public static final String TIFF = "image/tiff";