flink-core/src/main/java/org/apache/flink/types/SerializableOptional.java

/*
 * 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.types;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

import java.io.Serializable;
import java.util.NoSuchElementException;
import java.util.Optional;
import java.util.function.Consumer;
import java.util.function.Function;

/**
 * Serializable {@link Optional}.
 */
public final class SerializableOptional<T extends Serializable> implements Serializable {
	private static final long serialVersionUID = -3312769593551775940L;

	private static final SerializableOptional<?> EMPTY = new SerializableOptional<>(null);

	@Nullable
	private final T value;

	private SerializableOptional(@Nullable T value) {
		this.value = value;
	}

	public T get() {
		if (value == null) {
			throw new NoSuchElementException("No value present");
		}
		return value;
	}

	public boolean isPresent() {
		return value != null;
	}

	public void ifPresent(Consumer<? super T> consumer) {
		if (value != null) {
			consumer.accept(value);
		}
	}

	public <R> Optional<R> map(Function<? super T, ? extends R> mapper) {
		if (value == null) {
			return Optional.empty();
		} else {
			return Optional.ofNullable(mapper.apply(value));
		}
	}

	public static <T extends Serializable> SerializableOptional<T> of(@Nonnull T value) {
		return new SerializableOptional<>(value);
	}

	public static <T extends Serializable> SerializableOptional<T> ofNullable(@Nullable T value) {
		if (value == null) {
			return empty();
		} else {
			return of(value);
		}
	}

	@SuppressWarnings("unchecked")
	public static <T extends Serializable> SerializableOptional<T> empty() {
		return (SerializableOptional<T>) EMPTY;
	}
}