private long sum(Collection<Long> values) {
    long sum = 0L;
    for (Long value : values) {
      assertNotNull(value);
      sum += value;
    }
    return sum;
  }
Sums the collection of non-null numbers.
hbase-server/src/test/java/org/apache/hadoop/hbase/quotas/TestFileSystemUtilizationChore.java