javascalautils.OptionCompanion Maven / Gradle / Ivy
/**
* Copyright 2015 Peter Nerg
*
* Licensed 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 javascalautils;
/**
* Acts as a Scala type companion object for {@link Option}/{@link Some}/{@link None}.
* The primary purpose is to get the Scala feel of instantiating classes.
* In Scala you can define a companion object for a class, acting as a static reference/singleton for that class allowing you do define factory methods.
* One use case is to define methods with the same name as the class and let these methods invoke the constructor thus creating a nice way to create instances
* without using the word "new".
* This can be achieved in java by statically importing a method and then using it.
* The limitation is that classes may not have method with the same name as the class itself hence new companion classes have to be created.
* To be able to use it in a neat concise way one needs to statically import the method.
*
*
* import static javascalautils.OptionCompanion.Option;
* import static javascalautils.OptionCompanion.Some;
* import static javascalautils.OptionCompanion.None;
*
* Option<String> option = Option("Life is full of options");
* Option<String> some = Some("Some is never None");
* Option<String> none = None();
*
*
*
*
* @author Peter Nerg
* @since 1.3
*/
public final class OptionCompanion {
private OptionCompanion() {
}
/**
* Creates an instance of Option.
* If a null value is provided then {@link None} is returned, else {@link Some} containing the provided value.
* Best used in conjunction with statically importing this method.
*
*
* import static javascalautils.OptionCompanion.Option;
*
* Option<String> option = Option("Life is full of options");
*
*
*
*
* @param
* The type for the value this {@link Option} represents
* @param value
* The value this Option shall represent
* @return The Option representing the provided value
* @see Option#apply(Object)
* @since 1.3
*/
public static Option Option(T value) {
return Option.apply(value);
}
/**
* Creates an instance of {@link Some}.
* Best used in conjunction with statically importing this method.
*
*
* import static javascalautils.OptionCompanion.Some;
*
* Option<String> some = Some("Some is never None");
*
*
*
*
* @param
* The type for the value this {@link Some} represents
* @param value
* The value represented by this Some
* @return The Some representing the value
* @see Some#Some(Object)
* @since 1.3
*/
public static Some Some(T value) {
return new Some<>(value);
}
/**
* Returns an instance of {@link None}.
* In practice returns the singleton instance for {@link None}, never creates new instances.
* Best used in conjunction with statically importing this method.
*
*
* import static javascalautils.OptionCompanion.None;
*
* Option<String> none = None();
*
*
*
*
* @param
* The type for the value this {@link None} represents
*
* @return The singleton instance for {@link None}
* @see Option#None()
* @see Option#empty()
* @see Option#DEFAULT_NONE
* @since 1.3
*/
@SuppressWarnings("unchecked")
public static None None() {
return Option.DEFAULT_NONE;
}
}