diff --git a/library/src/main/java/com/panoramagl/downloaders/PLFileDownloaderListener.java b/library/src/main/java/com/panoramagl/downloaders/PLFileDownloaderListener.java
deleted file mode 100755
index 8b873f6..0000000
--- a/library/src/main/java/com/panoramagl/downloaders/PLFileDownloaderListener.java
+++ /dev/null
@@ -1,39 +0,0 @@
-/*
- * PanoramaGL library
- * Version 0.2 beta
- * Copyright (c) 2010 Javier Baez <javbaezga@gmail.com>
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package com.panoramagl.downloaders;
-
-public interface PLFileDownloaderListener {
-    /**
-     * download methods
-     */
-
-    void didBeginDownload(String url, long startTime);
-
-    void didProgressDownload(String url, int progress);
-
-    void didStopDownload(String url);
-
-    void didEndDownload(String url, byte[] data, long elapsedTime);
-
-    /**
-     * error methods
-     */
-
-    void didErrorDownload(String url, String error, int responseCode, byte[] data);
-}
\ No newline at end of file
diff --git a/library/src/main/java/com/panoramagl/downloaders/PLFileDownloaderListener.kt b/library/src/main/java/com/panoramagl/downloaders/PLFileDownloaderListener.kt
new file mode 100755
index 0000000..1a0ca07
--- /dev/null
+++ b/library/src/main/java/com/panoramagl/downloaders/PLFileDownloaderListener.kt
@@ -0,0 +1,13 @@
+package com.panoramagl.downloaders
+
+interface PLFileDownloaderListener {
+    fun didBeginDownload(url: String?, startTime: Long)
+
+    fun didProgressDownload(url: String?, progress: Int)
+
+    fun didStopDownload(url: String?)
+
+    fun didEndDownload(url: String?, data: ByteArray?, elapsedTime: Long)
+
+    fun didErrorDownload(url: String?, error: String?, responseCode: Int, data: ByteArray?)
+}
\ No newline at end of file
diff --git a/library/src/main/java/com/panoramagl/downloaders/PLIFileDownloaderManager.java b/library/src/main/java/com/panoramagl/downloaders/PLIFileDownloaderManager.java
deleted file mode 100755
index e4020e1..0000000
--- a/library/src/main/java/com/panoramagl/downloaders/PLIFileDownloaderManager.java
+++ /dev/null
@@ -1,47 +0,0 @@
-/*
- * PanoramaGL library
- * Version 0.2 beta
- * Copyright (c) 2010 Javier Baez <javbaezga@gmail.com>
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package com.panoramagl.downloaders;
-
-public interface PLIFileDownloaderManager {
-    /**
-     * property methods
-     */
-
-    boolean isRunning();
-
-    /**
-     * file downloaders methods
-     */
-
-    void add(PLIFileDownloader fileDownloader);
-
-    boolean remove(PLIFileDownloader fileDownloader);
-
-    boolean removeAll();
-
-    /**
-     * control methods
-     */
-
-    void download(PLIFileDownloader fileDownloader);
-
-    boolean start();
-
-    boolean stop();
-}
\ No newline at end of file
diff --git a/library/src/main/java/com/panoramagl/downloaders/PLIFileDownloaderManager.kt b/library/src/main/java/com/panoramagl/downloaders/PLIFileDownloaderManager.kt
new file mode 100755
index 0000000..f417e59
--- /dev/null
+++ b/library/src/main/java/com/panoramagl/downloaders/PLIFileDownloaderManager.kt
@@ -0,0 +1,17 @@
+package com.panoramagl.downloaders
+
+interface PLIFileDownloaderManager {
+    val isRunning: Boolean
+
+    fun add(fileDownloader: PLIFileDownloader?)
+
+    fun remove(fileDownloader: PLIFileDownloader?): Boolean
+
+    fun removeAll(): Boolean
+
+    fun download(fileDownloader: PLIFileDownloader?)
+
+    fun start(): Boolean
+
+    fun stop(): Boolean
+}
diff --git a/library/src/main/java/com/panoramagl/downloaders/PLLocalFileDownloader.kt b/library/src/main/java/com/panoramagl/downloaders/PLLocalFileDownloader.kt
index c3b80e0..9051562 100755
--- a/library/src/main/java/com/panoramagl/downloaders/PLLocalFileDownloader.kt
+++ b/library/src/main/java/com/panoramagl/downloaders/PLLocalFileDownloader.kt
@@ -46,7 +46,8 @@ class PLLocalFileDownloader(private var context: Context, url: String?, listener
                     val file = File(url.substring(7))
                     if (file.canRead()) `is` = FileInputStream(file)
                 }
-            } else throw PLRequestInvalidatedException(url)
+            } else
+                throw PLRequestInvalidatedException(url)
             if (this.isRunning) {
                 result = ByteArray(`is`!!.available())
                 `is`.read(result)
@@ -54,7 +55,8 @@ class PLLocalFileDownloader(private var context: Context, url: String?, listener
                     listener!!.didProgressDownload(url, 100)
                     listener.didEndDownload(url, result, System.currentTimeMillis() - startTime)
                 }
-            } else throw PLRequestInvalidatedException(url)
+            } else
+                throw PLRequestInvalidatedException(url)
         } catch (e: Throwable) {
             if (this.isRunning) {
                 Timber.e(e)
diff --git a/library/src/main/java/com/panoramagl/downloaders/PLRequestInvalidatedException.java b/library/src/main/java/com/panoramagl/downloaders/PLRequestInvalidatedException.java
deleted file mode 100755
index 663377a..0000000
--- a/library/src/main/java/com/panoramagl/downloaders/PLRequestInvalidatedException.java
+++ /dev/null
@@ -1,30 +0,0 @@
-/*
- * PanoramaGL library
- * Version 0.2 beta
- * Copyright (c) 2010 Javier Baez <javbaezga@gmail.com>
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package com.panoramagl.downloaders;
-
-@SuppressWarnings("serial")
-public class PLRequestInvalidatedException extends RuntimeException {
-    /**
-     * init methods
-     */
-
-    public PLRequestInvalidatedException(String url) {
-        super(String.format("Request to %s was invalidated", url));
-    }
-}
\ No newline at end of file
diff --git a/library/src/main/java/com/panoramagl/downloaders/PLRequestInvalidatedException.kt b/library/src/main/java/com/panoramagl/downloaders/PLRequestInvalidatedException.kt
new file mode 100755
index 0000000..ca0e005
--- /dev/null
+++ b/library/src/main/java/com/panoramagl/downloaders/PLRequestInvalidatedException.kt
@@ -0,0 +1,3 @@
+package com.panoramagl.downloaders
+
+class PLRequestInvalidatedException(url: String) : RuntimeException(String.format("Request to %s was invalidated", url))
\ No newline at end of file