diff --git a/core/src/main/java/com/taobao/arthas/core/command/monitor200/ThreadSampler.java b/core/src/main/java/com/taobao/arthas/core/command/monitor200/ThreadSampler.java
index 91fade566d3..ee75954a7a2 100644
--- a/core/src/main/java/com/taobao/arthas/core/command/monitor200/ThreadSampler.java
+++ b/core/src/main/java/com/taobao/arthas/core/command/monitor200/ThreadSampler.java
@@ -124,6 +124,7 @@ public int compare(ThreadVO o1, ThreadVO o2) {
 
         // Sort by CPU time : should be a rendering hint...
         Collections.sort(threads, new Comparator<ThreadVO>() {
+            @Override
             public int compare(ThreadVO o1, ThreadVO o2) {
                 long l1 = deltas.get(o1);
                 long l2 = deltas.get(o2);
diff --git a/core/src/main/java/com/taobao/arthas/core/util/FileUtils.java b/core/src/main/java/com/taobao/arthas/core/util/FileUtils.java
index ec046468cf2..c118a68b66f 100644
--- a/core/src/main/java/com/taobao/arthas/core/util/FileUtils.java
+++ b/core/src/main/java/com/taobao/arthas/core/util/FileUtils.java
@@ -140,7 +140,7 @@ public static void saveCommandHistory(List<int[]> history, File file) {
 
     public static List<int[]> loadCommandHistory(File file) {
         BufferedReader br = null;
-        List<int[]> history = new ArrayList<int[]>();
+        List<int[]> history = new ArrayList<>();
         try {
             br = new BufferedReader(new InputStreamReader(new FileInputStream(file)));
             String line;
@@ -194,7 +194,7 @@ public static void saveCommandHistoryString(List<String> history, File file) {
 
     public static List<String> loadCommandHistoryString(File file) {
         BufferedReader br = null;
-        List<String> history = new ArrayList<String>();
+        List<String> history = new ArrayList<>();
         try {
             br = new BufferedReader(new InputStreamReader(new FileInputStream(file), "utf-8"));
             String line;