fixed some warnings
diff --git a/modules/api/src/main/java/org/apache/fluo/api/config/SimpleConfiguration.java b/modules/api/src/main/java/org/apache/fluo/api/config/SimpleConfiguration.java
index 545f761..aa4c1eb 100644
--- a/modules/api/src/main/java/org/apache/fluo/api/config/SimpleConfiguration.java
+++ b/modules/api/src/main/java/org/apache/fluo/api/config/SimpleConfiguration.java
@@ -247,7 +247,7 @@
     Builder<String, String> builder = ImmutableMap.builder();
     Iterator<String> ki = getKeys();
     while (ki.hasNext()) {
-      String k = (String) ki.next();
+      String k = ki.next();
       builder.put(k, getRawString(k));
     }
 
diff --git a/modules/core/src/test/java/org/apache/fluo/core/observer/ObserverStoreTest.java b/modules/core/src/test/java/org/apache/fluo/core/observer/ObserverStoreTest.java
index 586d678..fd94a12 100644
--- a/modules/core/src/test/java/org/apache/fluo/core/observer/ObserverStoreTest.java
+++ b/modules/core/src/test/java/org/apache/fluo/core/observer/ObserverStoreTest.java
@@ -22,6 +22,7 @@
 import org.junit.Assert;
 import org.junit.Test;
 
+@SuppressWarnings("deprecation")
 public class ObserverStoreTest {
 
   @Test