address review comments

src/com/fsck/k9/activity/MessageCompose.java

@@ -1155,7 +1155,7 @@ public class MessageCompose extends K9Activity implements OnClickListener,
     @Override
     protected void onSaveInstanceState(Bundle outState) {
         super.onSaveInstanceState(outState);
-        List<Attachment> attachments = new ArrayList<Attachment>();
+        ArrayList<Attachment> attachments = new ArrayList<Attachment>();
         for (int i = 0, count = mAttachments.getChildCount(); i < count; i++) {
             View view = mAttachments.getChildAt(i);
             Attachment attachment = (Attachment) view.getTag();
@@ -1164,7 +1164,7 @@ public class MessageCompose extends K9Activity implements OnClickListener,
 
         outState.putInt(STATE_KEY_NUM_ATTACHMENTS_LOADING, mNumAttachmentsLoading);
         outState.putString(STATE_KEY_WAITING_FOR_ATTACHMENTS, mWaitingForAttachments.name());
-        outState.putParcelableArrayList(STATE_KEY_ATTACHMENTS, Utility.toArrayList(attachments));
+        outState.putParcelableArrayList(STATE_KEY_ATTACHMENTS, attachments);
         outState.putBoolean(STATE_KEY_CC_SHOWN, mCcWrapper.getVisibility() == View.VISIBLE);
         outState.putBoolean(STATE_KEY_BCC_SHOWN, mBccWrapper.getVisibility() == View.VISIBLE);
         outState.putSerializable(STATE_KEY_QUOTED_TEXT_MODE, mQuotedTextMode);

src/com/fsck/k9/activity/NotificationDeleteConfirmation.java

@@ -27,6 +27,9 @@ public class NotificationDeleteConfirmation extends Activity {
     private Account mAccount;
     private List<MessageReference> mMessageRefs;
 
+    /**
+     * @param refs must be Serializable
+     */
     public static PendingIntent getIntent(Context context, final Account account, final List<MessageReference> refs) {
         Intent i = new Intent(context, NotificationDeleteConfirmation.class);
         i.putExtra(EXTRA_ACCOUNT, account.getUuid());

src/com/fsck/k9/helper/Utility.java

@@ -708,34 +708,17 @@ public class Utility {
         return sMainThreadHandler;
     }
 
+    /**
+     * @return the supplied list casted to Serializable.
+     *
+     * See https://github.com/k9mail/k9mail_pgp_mime/pull/12#issuecomment-58767082
+     */
     public static <T> Serializable toSerializableList(List<T> list) {
-        return isExpectedCollectionClass(Serializable.class, list) ?
-                (Serializable) list :
-                new ArrayList<T>(list);
-    }
-
-    public static <T> ArrayList<T> toArrayList(List<T> list) {
-        return isExpectedCollectionClass(ArrayList.class, list) ?
-                (ArrayList<T>) list :
-                new ArrayList<T>(list);
+        return (Serializable) list;
     }
 
     public static <T, U> Serializable toSerializableConcurrentMap(ConcurrentMap<T, U> map) {
-        return isExpectedCollectionClass(ConcurrentHashMap.class, map) ?
-                (ConcurrentHashMap<T, U>) map :
-                new ConcurrentHashMap<T, U>(map);
-    }
-
-    private static boolean isExpectedCollectionClass(Class<?> expected, Object instance) {
-//        Objects.requireNonNull(instance); // uncomment when project moves to API level 19
-        if (!expected.isInstance(instance)) {
-            Log.w(K9.LOG_TAG, "Instance class [" + instance.getClass().getName()
-                    + "] would be better as [" + expected.getName()
-                    + "] for performance, to prevent collection copying");
-            return false;
-        } else {
-            return true;
-        }
+        return (ConcurrentHashMap<T, U>) map;
     }
 
 }

src/com/fsck/k9/service/NotificationActionService.java

@@ -37,6 +37,9 @@ public class NotificationActionService extends CoreService {
         return PendingIntent.getService(context, account.getAccountNumber(), i, PendingIntent.FLAG_UPDATE_CURRENT);
     }
 
+    /**
+     * @param refs must be Serializable
+     */
     public static PendingIntent getReadAllMessagesIntent(Context context, final Account account,
             final List<MessageReference> refs) {
         Intent i = new Intent(context, NotificationActionService.class);
@@ -55,6 +58,9 @@ public class NotificationActionService extends CoreService {
         return PendingIntent.getService(context, account.getAccountNumber(), i, PendingIntent.FLAG_UPDATE_CURRENT);
     }
 
+    /**
+     * @param refs must be Serializable
+     */
     public static Intent getDeleteAllMessagesIntent(Context context, final Account account,
             final List<MessageReference> refs) {
         Intent i = new Intent(context, NotificationActionService.class);

tests-on-jvm/src/com/fsck/k9/helper/UtilityTest.java

@@ -1,28 +0,0 @@
-package com.fsck.k9.mail.internet;
-
-import com.fsck.k9.helper.Utility;
-
-import junit.framework.TestCase;
-
-import java.io.*;
-import java.util.*;
-
-public class UtilityTest extends TestCase {
-
-    public void testToArrayList() {
-        LinkedList<String> input = new LinkedList<String>(Arrays.asList("a", "b"));
-
-        Serializable serializableList = Utility.toArrayList(input);
-
-        assertEquals(serializableList, input);
-    }
-
-    public void testToArrayListAlreadyArrayList() {
-        ArrayList<String> input = new ArrayList<String>(Arrays.asList("a", "b"));
-
-        Serializable serializableList = Utility.toArrayList(input);
-
-        assertSame(serializableList, input);
-    }
-
-}