diff --git a/Tethering/src/com/android/networkstack/tethering/BpfMap.java b/Tethering/src/com/android/networkstack/tethering/BpfMap.java
index 9505709..69ad1b6 100644
--- a/Tethering/src/com/android/networkstack/tethering/BpfMap.java
+++ b/Tethering/src/com/android/networkstack/tethering/BpfMap.java
@@ -134,7 +134,7 @@
      *
      * TODO: consider allowing null passed-in key.
      */
-    public K getNextKey(@Nullable K key) throws ErrnoException {
+    public K getNextKey(@NonNull K key) throws ErrnoException {
         Objects.requireNonNull(key);
         return getNextKeyInternal(key);
     }
@@ -185,14 +185,11 @@
      * Otherwise, iteration will result in undefined behaviour.
      */
     public void forEach(BiConsumer<K, V> action) throws ErrnoException {
-        @Nullable
-        K nextKey = getFirstKey();
+        @Nullable K nextKey = getFirstKey();
 
         while (nextKey != null) {
-            @NonNull
-            final K curKey = nextKey;
-            @NonNull
-            final V value = getValue(curKey);
+            @NonNull final K curKey = nextKey;
+            @NonNull final V value = getValue(curKey);
 
             nextKey = getNextKey(curKey);
             action.accept(curKey, value);
diff --git a/Tethering/tests/privileged/src/com/android/networkstack/tethering/BpfMapTest.java b/Tethering/tests/privileged/src/com/android/networkstack/tethering/BpfMapTest.java
index 77c0961..1ddbaa9 100644
--- a/Tethering/tests/privileged/src/com/android/networkstack/tethering/BpfMapTest.java
+++ b/Tethering/tests/privileged/src/com/android/networkstack/tethering/BpfMapTest.java
@@ -43,6 +43,7 @@
 
 import java.net.InetAddress;
 import java.util.NoSuchElementException;
+import java.util.concurrent.atomic.AtomicInteger;
 
 
 @RunWith(AndroidJUnit4.class)
@@ -96,7 +97,9 @@
             bpfMap.forEach((key, value) -> {
                 try {
                     assertTrue(bpfMap.deleteEntry(key));
-                } catch (ErrnoException ignored) { }
+                } catch (ErrnoException e) {
+                    fail("Fail to delete the key " + key + ": " + e);
+                }
             });
             assertNull(bpfMap.getFirstKey());
         }
@@ -284,15 +287,11 @@
     @Test
     public void testIterateEmptyMap() throws Exception {
         try (BpfMap<TetherIngressKey, TetherIngressValue> bpfMap = getTestMap()) {
-            // Use an one element array to be a trick for a counter because local variables
-            // referenced from a lambda expression must be final.
-            final int[] count = {0};
-            bpfMap.forEach((key, value) -> {
-                count[0]++;
-            });
-
-            // Expect that consumer has never be called.
-            assertEquals(0, count[0]);
+            // Can't use an int because variables used in a lambda must be final.
+            final AtomicInteger count = new AtomicInteger();
+            bpfMap.forEach((key, value) -> count.incrementAndGet());
+            // Expect that the consumer was never called.
+            assertEquals(0, count.get());
         }
     }
 
@@ -306,9 +305,8 @@
                 bpfMap.insertEntry(resultMap.keyAt(i), resultMap.valueAt(i));
             }
 
-            // Use an one element array to be a trick for a counter because local variables
-            // referenced from a lambda expression must be final.
-            final int[] count = {0};
+            // Can't use an int because variables used in a lambda must be final.
+            final AtomicInteger count = new AtomicInteger();
             bpfMap.forEach((key, value) -> {
                 try {
                     assertTrue(bpfMap.deleteEntry(key));
@@ -318,9 +316,9 @@
                 if (!value.equals(resultMap.remove(key))) {
                     fail("Unexpected result: " + key + ", value: " + value);
                 }
-                count[0]++;
+                count.incrementAndGet();
             });
-            assertEquals(3, count[0]);
+            assertEquals(3, count.get());
             assertTrue(resultMap.isEmpty());
             assertNull(bpfMap.getFirstKey());
         }