| /* |
| * 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.flink.api.common.functions; |
| |
| import org.apache.flink.annotation.Public; |
| |
| import java.io.Serializable; |
| |
| /** |
| * A filter function is a predicate applied individually to each record. |
| * The predicate decides whether to keep the element, or to discard it. |
| * <p> |
| * The basic syntax for using a FilterFunction is as follows: |
| * <pre>{@code |
| * DataSet<X> input = ...; |
| * |
| * DataSet<X> result = input.filter(new MyFilterFunction()); |
| * }</pre> |
| * <p> |
| * <strong>IMPORTANT:</strong> The system assumes that the function does not |
| * modify the elements on which the predicate is applied. Violating this assumption |
| * can lead to incorrect results. |
| * |
| * @param <T> The type of the filtered elements. |
| */ |
| @Public |
| public interface FilterFunction<T> extends Function, Serializable { |
| |
| /** |
| * The filter function that evaluates the predicate. |
| * <p> |
| * <strong>IMPORTANT:</strong> The system assumes that the function does not |
| * modify the elements on which the predicate is applied. Violating this assumption |
| * can lead to incorrect results. |
| * |
| * @param value The value to be filtered. |
| * @return True for values that should be retained, false for values to be filtered out. |
| * |
| * @throws Exception This method may throw exceptions. Throwing an exception will cause the operation |
| * to fail and may trigger recovery. |
| */ |
| boolean filter(T value) throws Exception; |
| } |