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<html>
<h2>Combine - Simple Function</h2>
<p>
  Combine is a Beam transform for combining collections of elements or values in your data.
  When you apply a Combine transform, you must provide the function that contains the logic for
  combining the elements or values. The combining function should be commutative and associative,
  as the function is not necessarily invoked exactly once on all values with a given key. Because
  the input data (including the value collection) may be distributed across multiple workers, the
  combining function might be called multiple times to perform partial combining on subsets of
  the value collection.
</p>
<p>
  Simple combine operations, such as sums, can usually be implemented as a simple function.
</p>
<p>
  <b>Kata:</b> Implement the summation of numbers using
  <a href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/transforms/SerializableFunction.html">
    Combine.globally(SerializableFunction)</a>.
</p>
<br>
<div class="hint">
  Implement the
  <a href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/transforms/SerializableFunction.html#apply-InputT-">
    SerializableFunction.apply</a> method that performs the summation of the Iterable.
</div>
<div class="hint">
  Refer to the Beam Programming Guide
  <a href="https://beam.apache.org/documentation/programming-guide/#simple-combines">
    "Simple combinations using simple functions"</a> section for more information.
</div>
</html>