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| <div class="sub-title"><span class="package-label-in-type">Package</span> <a href="package-summary.html">org.apache.kafka.streams.kstream</a></div> |
| <h1 title="Interface Reducer" class="title">Interface Reducer<V></h1> |
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| <dt>Type Parameters:</dt> |
| <dd><code>V</code> - value type</dd> |
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| <pre>public interface <span class="type-name-label">Reducer<V></span></pre> |
| <div class="block">The <code>Reducer</code> interface for combining two values of the same type into a new value. |
| In contrast to <a href="Aggregator.html" title="interface in org.apache.kafka.streams.kstream"><code>Aggregator</code></a> the result type must be the same as the input type. |
| <p> |
| The provided values can be either original values from input <a href="../KeyValue.html" title="class in org.apache.kafka.streams"><code>KeyValue</code></a> pair records or be a previously |
| computed result from <a href="#apply(V,V)"><code>apply(Object, Object)</code></a>. |
| <p> |
| <code>Reducer</code> can be used to implement aggregation functions like sum, min, or max.</div> |
| <dl class="notes"> |
| <dt>See Also:</dt> |
| <dd><a href="KGroupedStream.html#reduce(org.apache.kafka.streams.kstream.Reducer)"><code>KGroupedStream.reduce(Reducer)</code></a>, |
| <a href="KGroupedStream.html#reduce(org.apache.kafka.streams.kstream.Reducer,org.apache.kafka.streams.kstream.Materialized)"><code>KGroupedStream.reduce(Reducer, Materialized)</code></a>, |
| <a href="TimeWindowedKStream.html#reduce(org.apache.kafka.streams.kstream.Reducer)"><code>TimeWindowedKStream.reduce(Reducer)</code></a>, |
| <a href="TimeWindowedKStream.html#reduce(org.apache.kafka.streams.kstream.Reducer,org.apache.kafka.streams.kstream.Materialized)"><code>TimeWindowedKStream.reduce(Reducer, Materialized)</code></a>, |
| <a href="SessionWindowedKStream.html#reduce(org.apache.kafka.streams.kstream.Reducer)"><code>SessionWindowedKStream.reduce(Reducer)</code></a>, |
| <a href="SessionWindowedKStream.html#reduce(org.apache.kafka.streams.kstream.Reducer,org.apache.kafka.streams.kstream.Materialized)"><code>SessionWindowedKStream.reduce(Reducer, Materialized)</code></a>, |
| <a href="Aggregator.html" title="interface in org.apache.kafka.streams.kstream"><code>Aggregator</code></a></dd> |
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| <td class="col-first"><code><a href="Reducer.html" title="type parameter in Reducer">V</a></code></td> |
| <th class="col-second" scope="row"><code><span class="member-name-link"><a href="#apply(V,V)">apply</a></span>​(<a href="Reducer.html" title="type parameter in Reducer">V</a> value1, |
| <a href="Reducer.html" title="type parameter in Reducer">V</a> value2)</code></th> |
| <td class="col-last"> |
| <div class="block">Aggregate the two given values into a single one.</div> |
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| <section class="detail" id="apply(V,V)"> |
| <h3 id="apply(java.lang.Object,java.lang.Object)">apply</h3> |
| <div class="member-signature"><span class="return-type"><a href="Reducer.html" title="type parameter in Reducer">V</a></span> <span class="member-name">apply</span>​(<span class="parameters"><a href="Reducer.html" title="type parameter in Reducer">V</a> value1, |
| <a href="Reducer.html" title="type parameter in Reducer">V</a> value2)</span></div> |
| <div class="block">Aggregate the two given values into a single one.</div> |
| <dl class="notes"> |
| <dt>Parameters:</dt> |
| <dd><code>value1</code> - the first value for the aggregation</dd> |
| <dd><code>value2</code> - the second value for the aggregation</dd> |
| <dt>Returns:</dt> |
| <dd>the aggregated value</dd> |
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