diff --git a/app/core/src/test/java/com/fsck/k9/message/MessageBuilderTest.java b/app/core/src/test/java/com/fsck/k9/message/MessageBuilderTest.java
index 97b090bcd..f6ed38e00 100644
--- a/app/core/src/test/java/com/fsck/k9/message/MessageBuilderTest.java
+++ b/app/core/src/test/java/com/fsck/k9/message/MessageBuilderTest.java
@@ -404,7 +404,7 @@ public class MessageBuilderTest extends RobolectricTest {
                 .setIdentity(identity)
                 .setMessageFormat(SimpleMessageFormat.TEXT)
                 .setText(TEST_MESSAGE_TEXT)
-                .setAttachments(new ArrayList<Attachment>())
+                .setAttachments(new ArrayList<>())
                 .setSignature("signature")
                 .setQuoteStyle(QuoteStyle.PREFIX)
                 .setQuotedTextMode(QuotedTextMode.NONE)
diff --git a/app/k9mail/src/main/java/com/fsck/k9/external/MessageProvider.java b/app/k9mail/src/main/java/com/fsck/k9/external/MessageProvider.java
index 320b83e10..d3929ff5a 100644
--- a/app/k9mail/src/main/java/com/fsck/k9/external/MessageProvider.java
+++ b/app/k9mail/src/main/java/com/fsck/k9/external/MessageProvider.java
@@ -536,7 +536,7 @@ public class MessageProvider extends ContentProvider {
                 if (MessageColumns._ID.equals(field)) {
                     extractors.put(field, new IdExtractor());
                 } else if (MessageColumns._COUNT.equals(field)) {
-                    extractors.put(field, new CountExtractor<MessageInfoHolder>(count));
+                    extractors.put(field, new CountExtractor<>(count));
                 } else if (MessageColumns.SUBJECT.equals(field)) {
                     extractors.put(field, new SubjectExtractor());
                 } else if (MessageColumns.SENDER.equals(field)) {
diff --git a/app/ui/legacy/src/main/java/com/fsck/k9/activity/compose/AttachmentPresenter.java b/app/ui/legacy/src/main/java/com/fsck/k9/activity/compose/AttachmentPresenter.java
index 59b27ce9e..6f2f734e4 100644
--- a/app/ui/legacy/src/main/java/com/fsck/k9/activity/compose/AttachmentPresenter.java
+++ b/app/ui/legacy/src/main/java/com/fsck/k9/activity/compose/AttachmentPresenter.java
@@ -119,7 +119,7 @@ public class AttachmentPresenter {
     }
 
     public List<com.fsck.k9.message.Attachment> getAttachments() {
-        return new ArrayList<com.fsck.k9.message.Attachment>(attachments.values());
+        return new ArrayList<>(attachments.values());
     }
 
     public void onClickAddAttachment(RecipientPresenter recipientPresenter) {
diff --git a/app/ui/legacy/src/main/java/com/fsck/k9/activity/compose/RecipientLoader.java b/app/ui/legacy/src/main/java/com/fsck/k9/activity/compose/RecipientLoader.java
index cd0f09814..13ec8c0fc 100644
--- a/app/ui/legacy/src/main/java/com/fsck/k9/activity/compose/RecipientLoader.java
+++ b/app/ui/legacy/src/main/java/com/fsck/k9/activity/compose/RecipientLoader.java
@@ -381,7 +381,7 @@ public class RecipientLoader extends AsyncTaskLoader<List<Recipient>> {
             return recipients;
         }
 
-        fillContactDataFromCursor(cursor, recipients, new HashMap<String, Recipient>(), null, maxRecipients);
+        fillContactDataFromCursor(cursor, recipients, new HashMap<>(), null, maxRecipients);
 
         return recipients;
     }
diff --git a/mail/common/src/main/java/com/fsck/k9/mail/internet/MessageExtractor.java b/mail/common/src/main/java/com/fsck/k9/mail/internet/MessageExtractor.java
index d4d56843a..5d458d40e 100644
--- a/mail/common/src/main/java/com/fsck/k9/mail/internet/MessageExtractor.java
+++ b/mail/common/src/main/java/com/fsck/k9/mail/internet/MessageExtractor.java
@@ -234,7 +234,7 @@ public class MessageExtractor {
     public static List<Part> collectAttachments(Message message) throws MessagingException {
         try {
             List<Part> attachments = new ArrayList<>();
-            findViewablesAndAttachments(message, new ArrayList<Viewable>(), attachments);
+            findViewablesAndAttachments(message, new ArrayList<>(), attachments);
             return attachments;
         } catch (Exception e) {
             throw new MessagingException("Couldn't collect attachment parts", e);