| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.ignite.lang; |
| |
| import java.io.Serializable; |
| import java.util.Collection; |
| import org.jetbrains.annotations.Nullable; |
| |
| /** |
| * Defines generic reducer that collects multiple values and reduces them into one. |
| * Reducers are useful in computations when results from multiple remote jobs need |
| * to be reduced into one, e.g. {@link org.apache.ignite.IgniteCompute#call(Collection, IgniteReducer)} method. |
| * |
| * @param <E> Type of collected values. |
| * @param <R> Type of reduced value. |
| */ |
| public interface IgniteReducer<E, R> extends Serializable { |
| /** |
| * Collects given value. If this method returns {@code false} then {@link #reduce()} |
| * will be called right away. Otherwise caller will continue collecting until all |
| * values are processed. |
| * |
| * @param e Value to collect. |
| * @return {@code true} to continue collecting, {@code false} to instruct caller to stop |
| * collecting and call {@link #reduce()} method. |
| */ |
| public boolean collect(@Nullable E e); |
| |
| /** |
| * Reduces collected values into one. |
| * |
| * @return Reduced value. |
| */ |
| public R reduce(); |
| } |