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From StephanEwen <...@git.apache.org>
Subject [GitHub] flink pull request: [FLINK-3002] Add Either type to the Java API
Date Wed, 18 Nov 2015 13:35:13 GMT
Github user StephanEwen commented on a diff in the pull request:

    https://github.com/apache/flink/pull/1371#discussion_r45198787
  
    --- Diff: flink-java/src/main/java/org/apache/flink/api/java/typeutils/Either.java ---
    @@ -0,0 +1,147 @@
    +/*
    + * 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.typeutils;
    +
    +/**
    + * This type represents a value of one two possible types, Left or Right
    + * (a disjoint union), inspired by Scala's Either type.
    + *
    + * @param <L> the type of Left
    + * @param <R> the type of Right
    + */
    +public abstract class Either<L, R> {
    +
    +	/**
    +	 * Create a Left value of Either
    +	 */
    +	public static <L, R> Either<L, R> left(L value) {
    +		return new Left<L, R>(value);
    +	}
    +
    +	/**
    +	 * Create a Right value of Either
    +	 */
    +	public static <L, R> Either<L, R> right(R value) {
    +		return new Right<L, R>(value);
    +	}
    +
    +	/**
    +	 * Retrieve the Left value of Either.
    +	 * @return the Left value
    +	 * @throws IllegalStateException if called on a Right
    +	 */
    +	public abstract L left() throws IllegalStateException;
    +
    +	/**
    +	 * Retrieve the Right value of Either.
    +	 * @return the Right value
    +	 * @throws IllegalStateException if called on a Left
    +	 */
    +	public abstract R right() throws IllegalStateException;
    +
    +	/**
    +	 * 
    +	 * @return true if this is a Left value, false if this is a Right value
    +	 */
    +	public abstract boolean isLeft();
    --- End diff --
    
    You could even make this method final and implement it as `return getClass() == Left.class".
May get you a little bit of performance...


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