Use Long.hashCode(long) to avoid manual hash code calculation

Change-Id: I5f4aa8b80339a0c671ff2d12f8ba25dba023f220

@@ -44,7 +44,7 @@ public class IndexedLambda implements Lambda {
 
 
     @Override
     @Override
     public int hashCode() {
     public int hashCode() {
-        return (int) (index ^ (index >>> 32));
+        return Long.hashCode(index);
     }
     }
 
 
     @Override
     @Override