diff --git a/app/src/main/java/com/huanchengfly/tieba/api/retrofit/NullOnEmptyConverterFactory.java b/app/src/main/java/com/huanchengfly/tieba/api/retrofit/NullOnEmptyConverterFactory.java
deleted file mode 100644
index f54b2f37..00000000
--- a/app/src/main/java/com/huanchengfly/tieba/api/retrofit/NullOnEmptyConverterFactory.java
+++ /dev/null
@@ -1,19 +0,0 @@
-package com.huanchengfly.tieba.api.retrofit;
-
-import java.lang.annotation.Annotation;
-import java.lang.reflect.Type;
-
-import okhttp3.ResponseBody;
-import retrofit2.Converter;
-import retrofit2.Retrofit;
-
-public class NullOnEmptyConverterFactory extends Converter.Factory {
-    @Override
-    public Converter<ResponseBody, ?> responseBodyConverter(Type type, Annotation[] annotations, Retrofit retrofit) {
-        final Converter<ResponseBody, ?> delegate = retrofit.nextResponseBodyConverter(this, type, annotations);
-        return (Converter<ResponseBody, Object>) body -> {
-            if (body.contentLength() == 0) return null;
-            return delegate.convert(body);
-        };
-    }
-}
diff --git a/app/src/main/java/com/huanchengfly/tieba/api/retrofit/NullOnEmptyConverterFactory.kt b/app/src/main/java/com/huanchengfly/tieba/api/retrofit/NullOnEmptyConverterFactory.kt
new file mode 100644
index 00000000..8a3771dd
--- /dev/null
+++ b/app/src/main/java/com/huanchengfly/tieba/api/retrofit/NullOnEmptyConverterFactory.kt
@@ -0,0 +1,16 @@
+package com.huanchengfly.tieba.api.retrofit
+
+import okhttp3.ResponseBody
+import retrofit2.Converter
+import retrofit2.Retrofit
+import java.lang.reflect.Type
+
+class NullOnEmptyConverterFactory : Converter.Factory() {
+    override fun responseBodyConverter(type: Type, annotations: Array<Annotation>, retrofit: Retrofit): Converter<ResponseBody, *>? {
+        val delegate: Converter<ResponseBody, *> = retrofit.nextResponseBodyConverter<Any>(this, type, annotations)
+        return (Converter<ResponseBody, Any?> { body: ResponseBody ->
+            if (body.contentLength() == 0L) return@Converter null
+            delegate.convert(body)
+        })
+    }
+}
\ No newline at end of file