diff --git a/app/src/main/java/fr/free/nrw/commons/Media.java b/app/src/main/java/fr/free/nrw/commons/Media.java
index a1ae1cc84..1d07e9c16 100644
--- a/app/src/main/java/fr/free/nrw/commons/Media.java
+++ b/app/src/main/java/fr/free/nrw/commons/Media.java
@@ -142,7 +142,7 @@ public class Media implements Parcelable {
         return coordinates;
     }
 
-    public void setCoordinates(LatLng coordinates) {
+    public void setCoordinates(@Nullable LatLng coordinates) {
         this.coordinates = coordinates;
     }
 
@@ -201,7 +201,7 @@ public class Media implements Parcelable {
         this.filename = filename;
     }
 
-    public Media(Uri localUri, String imageUrl, String filename, String description, long dataLength, Date dateCreated, Date dateUploaded, String creator) {
+    public Media(Uri localUri, String imageUrl, String filename, String description, long dataLength, Date dateCreated, @Nullable Date dateUploaded, String creator) {
         this();
         this.localUri = localUri;
         this.imageUrl = imageUrl;
diff --git a/app/src/main/java/fr/free/nrw/commons/concurrency/ThreadPoolExecutorService.java b/app/src/main/java/fr/free/nrw/commons/concurrency/ThreadPoolExecutorService.java
index 1516d85d8..85f8cbfeb 100644
--- a/app/src/main/java/fr/free/nrw/commons/concurrency/ThreadPoolExecutorService.java
+++ b/app/src/main/java/fr/free/nrw/commons/concurrency/ThreadPoolExecutorService.java
@@ -39,7 +39,7 @@ public class ThreadPoolExecutorService implements Executor {
     }
 
     @Override
-    public void execute(Runnable command) {
+    public void execute(@NonNull Runnable command) {
         backgroundPool.execute(command);
     }
 
diff --git a/app/src/main/java/fr/free/nrw/commons/contributions/ContributionsContentProvider.java b/app/src/main/java/fr/free/nrw/commons/contributions/ContributionsContentProvider.java
index 9dc933358..6e84065f2 100644
--- a/app/src/main/java/fr/free/nrw/commons/contributions/ContributionsContentProvider.java
+++ b/app/src/main/java/fr/free/nrw/commons/contributions/ContributionsContentProvider.java
@@ -7,6 +7,7 @@ import android.database.Cursor;
 import android.database.sqlite.SQLiteDatabase;
 import android.database.sqlite.SQLiteQueryBuilder;
 import android.net.Uri;
+import android.support.annotation.NonNull;
 import android.text.TextUtils;
 
 import fr.free.nrw.commons.CommonsApplication;
@@ -38,7 +39,7 @@ public class ContributionsContentProvider extends ContentProvider{
     }
 
     @Override
-    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
+    public Cursor query(@NonNull Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
         SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
         queryBuilder.setTables(Contribution.Table.TABLE_NAME);
 
@@ -71,12 +72,12 @@ public class ContributionsContentProvider extends ContentProvider{
     }
 
     @Override
-    public String getType(Uri uri) {
+    public String getType(@NonNull Uri uri) {
         return null;
     }
 
     @Override
-    public Uri insert(Uri uri, ContentValues contentValues) {
+    public Uri insert(@NonNull Uri uri, ContentValues contentValues) {
         int uriType = uriMatcher.match(uri);
         SQLiteDatabase sqlDB = CommonsApplication.getInstance().getDBOpenHelper().getWritableDatabase();
         long id = 0;
@@ -92,7 +93,7 @@ public class ContributionsContentProvider extends ContentProvider{
     }
 
     @Override
-    public int delete(Uri uri, String s, String[] strings) {
+    public int delete(@NonNull Uri uri, String s, String[] strings) {
         int rows = 0;
         int uriType = uriMatcher.match(uri);
 
@@ -114,7 +115,7 @@ public class ContributionsContentProvider extends ContentProvider{
     }
 
     @Override
-    public int bulkInsert(Uri uri, ContentValues[] values) {
+    public int bulkInsert(@NonNull Uri uri, @NonNull ContentValues[] values) {
         Timber.d("Hello, bulk insert! (ContributionsContentProvider)");
         int uriType = uriMatcher.match(uri);
         SQLiteDatabase sqlDB = CommonsApplication.getInstance().getDBOpenHelper().getWritableDatabase();
@@ -136,7 +137,7 @@ public class ContributionsContentProvider extends ContentProvider{
     }
 
     @Override
-    public int update(Uri uri, ContentValues contentValues, String selection, String[] selectionArgs) {
+    public int update(@NonNull Uri uri, ContentValues contentValues, String selection, String[] selectionArgs) {
         /*
         SQL Injection warnings: First, note that we're not exposing this to the outside world (exported="false")
         Even then, we should make sure to sanitize all user input appropriately. Input that passes through ContentValues
diff --git a/app/src/main/java/fr/free/nrw/commons/contributions/ContributionsListFragment.java b/app/src/main/java/fr/free/nrw/commons/contributions/ContributionsListFragment.java
index c009243b9..bcbb5a739 100644
--- a/app/src/main/java/fr/free/nrw/commons/contributions/ContributionsListFragment.java
+++ b/app/src/main/java/fr/free/nrw/commons/contributions/ContributionsListFragment.java
@@ -8,6 +8,7 @@ import android.content.SharedPreferences;
 import android.content.pm.PackageManager;
 import android.os.Build;
 import android.os.Bundle;
+import android.support.annotation.NonNull;
 import android.support.v4.app.Fragment;
 import android.support.v4.content.ContextCompat;
 import android.support.v7.app.AlertDialog;
@@ -162,7 +163,7 @@ public class ContributionsListFragment extends Fragment {
     }
 
     @Override
-    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
+    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
 
         Timber.d("onRequestPermissionsResult: req code = " + " perm = " + permissions + " grant =" + grantResults);
 
diff --git a/app/src/main/java/fr/free/nrw/commons/modifications/ModificationsContentProvider.java b/app/src/main/java/fr/free/nrw/commons/modifications/ModificationsContentProvider.java
index 9c9421864..11caa94fa 100644
--- a/app/src/main/java/fr/free/nrw/commons/modifications/ModificationsContentProvider.java
+++ b/app/src/main/java/fr/free/nrw/commons/modifications/ModificationsContentProvider.java
@@ -7,6 +7,7 @@ import android.database.Cursor;
 import android.database.sqlite.SQLiteDatabase;
 import android.database.sqlite.SQLiteQueryBuilder;
 import android.net.Uri;
+import android.support.annotation.NonNull;
 import android.text.TextUtils;
 
 import fr.free.nrw.commons.CommonsApplication;
@@ -39,7 +40,7 @@ public class ModificationsContentProvider extends ContentProvider{
     }
 
     @Override
-    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
+    public Cursor query(@NonNull Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
         SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
         queryBuilder.setTables(ModifierSequence.Table.TABLE_NAME);
 
@@ -61,12 +62,12 @@ public class ModificationsContentProvider extends ContentProvider{
     }
 
     @Override
-    public String getType(Uri uri) {
+    public String getType(@NonNull Uri uri) {
         return null;
     }
 
     @Override
-    public Uri insert(Uri uri, ContentValues contentValues) {
+    public Uri insert(@NonNull Uri uri, ContentValues contentValues) {
         int uriType = uriMatcher.match(uri);
         SQLiteDatabase sqlDB = CommonsApplication.getInstance().getDBOpenHelper().getWritableDatabase();
         long id = 0;
@@ -82,7 +83,7 @@ public class ModificationsContentProvider extends ContentProvider{
     }
 
     @Override
-    public int delete(Uri uri, String s, String[] strings) {
+    public int delete(@NonNull Uri uri, String s, String[] strings) {
         int uriType = uriMatcher.match(uri);
         SQLiteDatabase sqlDB = CommonsApplication.getInstance().getDBOpenHelper().getWritableDatabase();
         switch (uriType) {
@@ -99,7 +100,7 @@ public class ModificationsContentProvider extends ContentProvider{
     }
 
     @Override
-    public int bulkInsert(Uri uri, ContentValues[] values) {
+    public int bulkInsert(@NonNull Uri uri, @NonNull ContentValues[] values) {
         Timber.d("Hello, bulk insert! (ModificationsContentProvider)");
         int uriType = uriMatcher.match(uri);
         SQLiteDatabase sqlDB = CommonsApplication.getInstance().getDBOpenHelper().getWritableDatabase();
@@ -121,7 +122,7 @@ public class ModificationsContentProvider extends ContentProvider{
     }
 
     @Override
-    public int update(Uri uri, ContentValues contentValues, String selection, String[] selectionArgs) {
+    public int update(@NonNull Uri uri, ContentValues contentValues, String selection, String[] selectionArgs) {
         /*
         SQL Injection warnings: First, note that we're not exposing this to the outside world (exported="false")
         Even then, we should make sure to sanitize all user input appropriately. Input that passes through ContentValues
diff --git a/app/src/main/java/fr/free/nrw/commons/upload/MultipleShareActivity.java b/app/src/main/java/fr/free/nrw/commons/upload/MultipleShareActivity.java
index 6955caef2..1ab00c88f 100644
--- a/app/src/main/java/fr/free/nrw/commons/upload/MultipleShareActivity.java
+++ b/app/src/main/java/fr/free/nrw/commons/upload/MultipleShareActivity.java
@@ -11,6 +11,7 @@ import android.database.DataSetObserver;
 import android.net.Uri;
 import android.os.Build;
 import android.os.Bundle;
+import android.support.annotation.NonNull;
 import android.support.v4.app.ActivityCompat;
 import android.support.v4.app.FragmentManager;
 import android.support.v4.content.ContextCompat;
@@ -105,7 +106,7 @@ public  class       MultipleShareActivity
     }
 
     @Override
-    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
+    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
         if (requestCode == 1 && grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
             multipleUploadBegins();
         }
diff --git a/app/src/main/java/fr/free/nrw/commons/upload/ShareActivity.java b/app/src/main/java/fr/free/nrw/commons/upload/ShareActivity.java
index 19e2d6925..1ce86a86a 100644
--- a/app/src/main/java/fr/free/nrw/commons/upload/ShareActivity.java
+++ b/app/src/main/java/fr/free/nrw/commons/upload/ShareActivity.java
@@ -9,6 +9,7 @@ import android.os.Build;
 import android.os.Bundle;
 import android.os.Environment;
 import android.os.ParcelFileDescriptor;
+import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
 import android.support.annotation.RequiresApi;
 import android.support.design.widget.Snackbar;
@@ -318,7 +319,7 @@ public  class       ShareActivity
 
     @Override
     public void onRequestPermissionsResult(int requestCode,
-                                           String[] permissions, int[] grantResults) {
+                                           @NonNull String[] permissions, @NonNull int[] grantResults) {
         switch (requestCode) {
             case REQUEST_PERM_ON_CREATE_STORAGE: {
                 if (grantResults.length >= 1