Have NetworkStats implements iterable

Make NetworkStats be iterable and expose iterator as system API
which is better than expose size() and getValues().
This API could be used by the caller who needs to get entry
from NetworkStats.

Bug: 210073043
CTS-Coverage-Bug: 215061403
Test: build, TH
Change-Id: I6cb4c8f63d7067133f2722b2be7e16b4098a697d

framework-t/src/android/net/NetworkStats.java

@@ -41,6 +41,7 @@ import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.util.Arrays;
 import java.util.HashSet;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -57,7 +58,7 @@ import java.util.function.Predicate;
  */
 // @NotThreadSafe
 @SystemApi
-public final class NetworkStats implements Parcelable {
+public final class NetworkStats implements Parcelable, Iterable<NetworkStats.Entry> {
     private static final String TAG = "NetworkStats";
 
     /**
@@ -677,6 +678,35 @@ public final class NetworkStats implements Parcelable {
         operations[i] = entry.operations;
     }
 
+    /**
+     * Iterate over Entry objects.
+     *
+     * Return an iterator of this object that will iterate through all contained Entry objects.
+     *
+     * This iterator does not support concurrent modification and makes no guarantee of fail-fast
+     * behavior. If any method that can mutate the contents of this object is called while
+     * iteration is in progress, either inside the loop or in another thread, then behavior is
+     * undefined.
+     * The remove() method is not implemented and will throw UnsupportedOperationException.
+     * @hide
+     */
+    @SystemApi
+    @NonNull public Iterator<Entry> iterator() {
+        return new Iterator<Entry>() {
+            int mIndex = 0;
+
+            @Override
+            public boolean hasNext() {
+                return mIndex < size;
+            }
+
+            @Override
+            public Entry next() {
+                return getValues(mIndex++, null);
+            }
+        };
+    }
+
     /**
      * Return specific stats entry.
      * @hide