src/com/wentch/redkale/source/Flipper.java

@@ -91,10 +91,11 @@ public final class Flipper implements Serializable {
         return sort;
     }
 
-    public void putSortIfEmpty(String sort) {
+    public Flipper putSortIfEmpty(String sort) {
         if (this.sort == null || this.sort.isEmpty()) {
             this.sort = sort;
         }
+        return this;
     }
 
     public void setSort(String sort) {