diff --git a/ui/src/main/java/com/wireguard/android/util/ClipboardUtils.java b/ui/src/main/java/com/wireguard/android/util/ClipboardUtils.java
deleted file mode 100644
index e9f65c59..00000000
--- a/ui/src/main/java/com/wireguard/android/util/ClipboardUtils.java
+++ /dev/null
@@ -1,40 +0,0 @@
-/*
- * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
- * SPDX-License-Identifier: Apache-2.0
- */
-
-package com.wireguard.android.util;
-
-import android.content.ClipData;
-import android.content.ClipboardManager;
-import android.content.Context;
-import android.view.View;
-import android.widget.TextView;
-
-import com.google.android.material.snackbar.Snackbar;
-import com.wireguard.util.NonNullForAll;
-
-/**
- * Standalone utilities for interacting with the system clipboard.
- */
-
-@NonNullForAll
-public final class ClipboardUtils {
-    private ClipboardUtils() {
-        // Prevent instantiation
-    }
-
-    public static void copyTextView(final View view) {
-        if (!(view instanceof TextView))
-            return;
-        final CharSequence text = ((TextView) view).getText();
-        if (text == null || text.length() == 0)
-            return;
-        final Object service = view.getContext().getSystemService(Context.CLIPBOARD_SERVICE);
-        if (!(service instanceof ClipboardManager))
-            return;
-        final CharSequence description = view.getContentDescription();
-        ((ClipboardManager) service).setPrimaryClip(ClipData.newPlainText(description, text));
-        Snackbar.make(view, description + " copied to clipboard", Snackbar.LENGTH_LONG).show();
-    }
-}
diff --git a/ui/src/main/java/com/wireguard/android/util/ClipboardUtils.kt b/ui/src/main/java/com/wireguard/android/util/ClipboardUtils.kt
new file mode 100644
index 00000000..c1ddaa4c
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/util/ClipboardUtils.kt
@@ -0,0 +1,30 @@
+/*
+ * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package com.wireguard.android.util
+
+import android.content.ClipData
+import android.content.ClipboardManager
+import android.content.Context
+import android.view.View
+import android.widget.TextView
+import com.google.android.material.snackbar.Snackbar
+
+/**
+ * Standalone utilities for interacting with the system clipboard.
+ */
+object ClipboardUtils {
+    @JvmStatic
+    fun copyTextView(view: View) {
+        if (view !is TextView)
+            return
+        val text = view.text
+        if (text == null || text.length == 0) return
+        val service = view.getContext().getSystemService(Context.CLIPBOARD_SERVICE) as? ClipboardManager
+                ?: return
+        val description = view.getContentDescription()
+        service.setPrimaryClip(ClipData.newPlainText(description, text))
+        Snackbar.make(view, "$description copied to clipboard", Snackbar.LENGTH_LONG).show()
+    }
+}
diff --git a/ui/src/main/java/com/wireguard/android/util/DownloadsFileSaver.java b/ui/src/main/java/com/wireguard/android/util/DownloadsFileSaver.java
deleted file mode 100644
index 14895b64..00000000
--- a/ui/src/main/java/com/wireguard/android/util/DownloadsFileSaver.java
+++ /dev/null
@@ -1,108 +0,0 @@
-/*
- * Copyright © 2019 WireGuard LLC. All Rights Reserved.
- * SPDX-License-Identifier: Apache-2.0
- */
-
-package com.wireguard.android.util;
-
-import android.content.ContentResolver;
-import android.content.ContentValues;
-import android.content.Context;
-import android.database.Cursor;
-import android.net.Uri;
-import android.os.Build;
-import android.os.Environment;
-import android.provider.MediaStore;
-import android.provider.MediaStore.MediaColumns;
-
-import com.wireguard.android.R;
-import com.wireguard.util.NonNullForAll;
-
-import java.io.File;
-import java.io.FileOutputStream;
-import java.io.IOException;
-import java.io.OutputStream;
-
-@NonNullForAll
-public final class DownloadsFileSaver {
-
-    private DownloadsFileSaver() {
-        // Prevent instantiation
-    }
-
-    public static DownloadsFile save(final Context context, final String name, final String mimeType, final boolean overwriteExisting) throws Exception {
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
-            final ContentResolver contentResolver = context.getContentResolver();
-            if (overwriteExisting)
-                contentResolver.delete(MediaStore.Downloads.EXTERNAL_CONTENT_URI, String.format("%s = ?", MediaColumns.DISPLAY_NAME), new String[]{name});
-            final ContentValues contentValues = new ContentValues();
-            contentValues.put(MediaColumns.DISPLAY_NAME, name);
-            contentValues.put(MediaColumns.MIME_TYPE, mimeType);
-            final Uri contentUri = contentResolver.insert(MediaStore.Downloads.EXTERNAL_CONTENT_URI, contentValues);
-            if (contentUri == null)
-                throw new IOException(context.getString(R.string.create_downloads_file_error));
-            final OutputStream contentStream = contentResolver.openOutputStream(contentUri);
-            if (contentStream == null)
-                throw new IOException(context.getString(R.string.create_downloads_file_error));
-            @SuppressWarnings("deprecation")
-            Cursor cursor = contentResolver.query(contentUri, new String[]{MediaColumns.DATA}, null, null, null);
-            String path = null;
-            if (cursor != null) {
-                try {
-                    if (cursor.moveToFirst())
-                        path = cursor.getString(0);
-                } finally {
-                    cursor.close();
-                }
-            }
-            if (path == null) {
-                path = "Download/";
-                cursor = contentResolver.query(contentUri, new String[]{MediaColumns.DISPLAY_NAME}, null, null, null);
-                if (cursor != null) {
-                    try {
-                        if (cursor.moveToFirst())
-                            path += cursor.getString(0);
-                    } finally {
-                        cursor.close();
-                    }
-                }
-            }
-            return new DownloadsFile(context, contentStream, path, contentUri);
-        } else {
-            @SuppressWarnings("deprecation") final File path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
-            final File file = new File(path, name);
-            if (!path.isDirectory() && !path.mkdirs())
-                throw new IOException(context.getString(R.string.create_output_dir_error));
-            return new DownloadsFile(context, new FileOutputStream(file), file.getAbsolutePath(), null);
-        }
-    }
-
-    public static final class DownloadsFile {
-        private final Context context;
-        private final String fileName;
-        private final OutputStream outputStream;
-        private final Uri uri;
-
-        private DownloadsFile(final Context context, final OutputStream outputStream, final String fileName, final Uri uri) {
-            this.context = context;
-            this.outputStream = outputStream;
-            this.fileName = fileName;
-            this.uri = uri;
-        }
-
-        public void delete() {
-            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q)
-                context.getContentResolver().delete(uri, null, null);
-            else
-                new File(fileName).delete();
-        }
-
-        public String getFileName() {
-            return fileName;
-        }
-
-        public OutputStream getOutputStream() {
-            return outputStream;
-        }
-    }
-}
diff --git a/ui/src/main/java/com/wireguard/android/util/DownloadsFileSaver.kt b/ui/src/main/java/com/wireguard/android/util/DownloadsFileSaver.kt
new file mode 100644
index 00000000..a0f0e1fb
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/util/DownloadsFileSaver.kt
@@ -0,0 +1,72 @@
+/*
+ * Copyright © 2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package com.wireguard.android.util
+
+import android.content.ContentValues
+import android.content.Context
+import android.net.Uri
+import android.os.Build
+import android.os.Environment
+import android.provider.MediaStore
+import android.provider.MediaStore.MediaColumns
+import com.wireguard.android.R
+import java.io.File
+import java.io.FileOutputStream
+import java.io.IOException
+import java.io.OutputStream
+
+object DownloadsFileSaver {
+    @Throws(Exception::class)
+    fun save(context: Context, name: String, mimeType: String?, overwriteExisting: Boolean) = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
+        val contentResolver = context.contentResolver
+        if (overwriteExisting)
+            contentResolver.delete(MediaStore.Downloads.EXTERNAL_CONTENT_URI, String.format("%s = ?", MediaColumns.DISPLAY_NAME), arrayOf(name))
+        val contentValues = ContentValues()
+        contentValues.put(MediaColumns.DISPLAY_NAME, name)
+        contentValues.put(MediaColumns.MIME_TYPE, mimeType)
+        val contentUri = contentResolver.insert(MediaStore.Downloads.EXTERNAL_CONTENT_URI, contentValues)
+                ?: throw IOException(context.getString(R.string.create_downloads_file_error))
+        val contentStream = contentResolver.openOutputStream(contentUri)
+                ?: throw IOException(context.getString(R.string.create_downloads_file_error))
+        @Suppress("DEPRECATION") var cursor = contentResolver.query(contentUri, arrayOf(MediaColumns.DATA), null, null, null)
+        var path: String? = null
+        if (cursor != null) {
+            try {
+                if (cursor.moveToFirst())
+                    path = cursor.getString(0)
+            } finally {
+                cursor.close()
+            }
+        }
+        if (path == null) {
+            path = "Download/"
+            cursor = contentResolver.query(contentUri, arrayOf(MediaColumns.DISPLAY_NAME), null, null, null)
+            if (cursor != null) {
+                try {
+                    if (cursor.moveToFirst())
+                        path += cursor.getString(0)
+                } finally {
+                    cursor.close()
+                }
+            }
+        }
+        DownloadsFile(context, contentStream, path, contentUri)
+    } else {
+        @Suppress("DEPRECATION") val path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS)
+        val file = File(path, name)
+        if (!path.isDirectory && !path.mkdirs())
+            throw IOException(context.getString(R.string.create_output_dir_error))
+        DownloadsFile(context, FileOutputStream(file), file.absolutePath, null)
+    }
+
+    class DownloadsFile(private val context: Context, val outputStream: OutputStream, val fileName: String, private val uri: Uri?) {
+        fun delete() {
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q)
+                context.contentResolver.delete(uri!!, null, null)
+            else
+                File(fileName).delete()
+        }
+    }
+}