Github user fhueske commented on a diff in the pull request: https://github.com/apache/flink/pull/1097#discussion_r39492448 --- Diff: flink-java/src/main/java/org/apache/flink/api/java/utils/Option.java --- @@ -0,0 +1,129 @@ +/* + * 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.java.utils; + +import java.util.Collections; +import java.util.HashSet; +import java.util.Set; + +/** + * Internal representation of a parameter passed to a user defined function. + */ +public class Option<T> { + + private String longName; + private String shortName; + + private T defaultValue; + private Set<T> choices; + + private String helpText; + + public Option(String name) { + this.longName = name; + this.choices = new HashSet<>(); + } + + /** + * Define a alternative / short name of the Parameter. + * + * @param shortName - short version of the parameter name + * @return the updated Option + */ + public Option<T> alt(String shortName) { + this.shortName = shortName; + return this; + } + + /** + * Define a default value for the option. + * + * Throws an exception if the list of possible values for the parameter is not empty and the default value passed + * is not in the list. + * + * @param defaultValue - the default value + * @return the updated Option + */ + public Option<T> defaultValue(T defaultValue) { + if (this.choices.isEmpty()) { + return this.setDefaultValue(defaultValue); + } else { + if (this.choices.contains(defaultValue)) { + return this.setDefaultValue(defaultValue); + } else { + throw new IllegalArgumentException("defaultValue passed is not in the list of expected values."); + } + } + } + + /** + * Restrict the list of possible values of the parameter. + * + * @param choices - the allowed values of the parameter. + * @return the updated Option + */ + public Option<T> choices(T... choices) { + Collections.addAll(this.choices, choices); --- End diff -- Add check that `defaultValue` (if already set) is in choices.
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