diff --git a/library/src/main/java/com/cundong/recyclerview/EndlessRecyclerOnScrollListener.java b/library/src/main/java/com/cundong/recyclerview/EndlessRecyclerOnScrollListener.java
index 9d6a5f1..ae5da18 100644
--- a/library/src/main/java/com/cundong/recyclerview/EndlessRecyclerOnScrollListener.java
+++ b/library/src/main/java/com/cundong/recyclerview/EndlessRecyclerOnScrollListener.java
@@ -67,6 +67,8 @@ public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                 staggeredGridLayoutManager.findLastVisibleItemPositions(lastPositions);
                 lastVisibleItemPosition = findMax(lastPositions);
                 break;
+            default:
+                break;
         }
     }
 
diff --git a/library/src/main/java/com/cundong/recyclerview/HeaderAndFooterRecyclerViewAdapter.java b/library/src/main/java/com/cundong/recyclerview/HeaderAndFooterRecyclerViewAdapter.java
index 3a13e73..34111e4 100644
--- a/library/src/main/java/com/cundong/recyclerview/HeaderAndFooterRecyclerViewAdapter.java
+++ b/library/src/main/java/com/cundong/recyclerview/HeaderAndFooterRecyclerViewAdapter.java
@@ -72,8 +72,7 @@ public HeaderAndFooterRecyclerViewAdapter(RecyclerView.Adapter innerAdapter) {
      */
     public void setAdapter(RecyclerView.Adapter<RecyclerView.ViewHolder> adapter) {
 
-        if (adapter != null) {
-            if (!(adapter instanceof RecyclerView.Adapter))
+        if (adapter != null&&!(adapter instanceof RecyclerView.Adapter)) {
                 throw new RuntimeException("your adapter must be a RecyclerView.Adapter");
         }
 
diff --git a/library/src/main/java/com/cundong/recyclerview/RecyclerViewUtils.java b/library/src/main/java/com/cundong/recyclerview/RecyclerViewUtils.java
index 234d02d..8225d7c 100644
--- a/library/src/main/java/com/cundong/recyclerview/RecyclerViewUtils.java
+++ b/library/src/main/java/com/cundong/recyclerview/RecyclerViewUtils.java
@@ -75,14 +75,10 @@ public static void removeFooterView(RecyclerView recyclerView) {
     public static void removeHeaderView(RecyclerView recyclerView) {
 
         RecyclerView.Adapter outerAdapter = recyclerView.getAdapter();
-
-        if (outerAdapter != null && outerAdapter instanceof HeaderAndFooterRecyclerViewAdapter) {
-
-            int headerViewCounter = ((HeaderAndFooterRecyclerViewAdapter) outerAdapter).getHeaderViewsCount();
-            if (headerViewCounter > 0) {
-                View headerView = ((HeaderAndFooterRecyclerViewAdapter) outerAdapter).getHeaderView();
-                ((HeaderAndFooterRecyclerViewAdapter) outerAdapter).removeFooterView(headerView);
-            }
+        int headerViewCounter = ((HeaderAndFooterRecyclerViewAdapter) outerAdapter).getHeaderViewsCount();
+        if (outerAdapter != null && outerAdapter instanceof HeaderAndFooterRecyclerViewAdapter && headerViewCounter > 0) {
+            View headerView = ((HeaderAndFooterRecyclerViewAdapter) outerAdapter).getHeaderView();
+            ((HeaderAndFooterRecyclerViewAdapter) outerAdapter).removeFooterView(headerView);
         }
     }
 
@@ -95,12 +91,9 @@ public static void removeHeaderView(RecyclerView recyclerView) {
      */
     public static int getLayoutPosition(RecyclerView recyclerView, RecyclerView.ViewHolder holder) {
         RecyclerView.Adapter outerAdapter = recyclerView.getAdapter();
-        if (outerAdapter != null && outerAdapter instanceof HeaderAndFooterRecyclerViewAdapter) {
-
-            int headerViewCounter = ((HeaderAndFooterRecyclerViewAdapter) outerAdapter).getHeaderViewsCount();
-            if (headerViewCounter > 0) {
-                return holder.getLayoutPosition() - headerViewCounter;
-            }
+        int headerViewCounter = ((HeaderAndFooterRecyclerViewAdapter) outerAdapter).getHeaderViewsCount();
+        if (outerAdapter != null && outerAdapter instanceof HeaderAndFooterRecyclerViewAdapter && headerViewCounter > 0) {
+            return holder.getLayoutPosition() - headerViewCounter;
         }
 
         return holder.getLayoutPosition();
diff --git a/sample/src/main/java/com/cundong/recyclerview/sample/EndlessGridLayoutActivity.java b/sample/src/main/java/com/cundong/recyclerview/sample/EndlessGridLayoutActivity.java
index d3b1f4d..baf0955 100644
--- a/sample/src/main/java/com/cundong/recyclerview/sample/EndlessGridLayoutActivity.java
+++ b/sample/src/main/java/com/cundong/recyclerview/sample/EndlessGridLayoutActivity.java
@@ -151,6 +151,8 @@ public void handleMessage(Message msg) {
                 case -3:
                     RecyclerViewStateUtils.setFooterViewState(activity, activity.mRecyclerView, REQUEST_COUNT, LoadingFooter.State.NetWorkError, activity.mFooterClick);
                     break;
+                default:
+                    break;
             }
         }
     }
diff --git a/sample/src/main/java/com/cundong/recyclerview/sample/EndlessLinearLayoutActivity.java b/sample/src/main/java/com/cundong/recyclerview/sample/EndlessLinearLayoutActivity.java
index e06722d..f8306bd 100644
--- a/sample/src/main/java/com/cundong/recyclerview/sample/EndlessLinearLayoutActivity.java
+++ b/sample/src/main/java/com/cundong/recyclerview/sample/EndlessLinearLayoutActivity.java
@@ -157,6 +157,8 @@ public void handleMessage(Message msg) {
                 case -3:
                     RecyclerViewStateUtils.setFooterViewState(activity, activity.mRecyclerView, REQUEST_COUNT, LoadingFooter.State.NetWorkError, activity.mFooterClick);
                     break;
+                default:
+                    break;
             }
         }
     }
diff --git a/sample/src/main/java/com/cundong/recyclerview/sample/EndlessStaggeredGridLayoutActivity.java b/sample/src/main/java/com/cundong/recyclerview/sample/EndlessStaggeredGridLayoutActivity.java
index 9f1d317..b9892d2 100644
--- a/sample/src/main/java/com/cundong/recyclerview/sample/EndlessStaggeredGridLayoutActivity.java
+++ b/sample/src/main/java/com/cundong/recyclerview/sample/EndlessStaggeredGridLayoutActivity.java
@@ -152,6 +152,8 @@ public void handleMessage(Message msg) {
                 case -3:
                     RecyclerViewStateUtils.setFooterViewState(activity, activity.mRecyclerView, REQUEST_COUNT, LoadingFooter.State.NetWorkError, activity.mFooterClick);
                     break;
+                default:
+                    break;
             }
         }
     }