javascalautils.Projection 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;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.function.Supplier;
import java.util.stream.Stream;
/**
* Abstract base class for the projections used by {@link Either}.
*
* @author Peter Nerg
* @since 1.1
*/
abstract class Projection implements Iterable {
/**
* Returns the value of the Right/Left in {@link Some} side in case the projection matches the side, else {@link None}.
* That is:
* If this is a {@link RightProjection} with a {@link Right}
* or
* If this is a {@link LeftProjection} with a {@link Left}.
* Then then return {@link Some} containing the value of the {@link Left}/{@link Right}.
* Any other case, return {@link None}.
*
* @return The Option
*/
public Option asOption() {
return Option.apply(orNull());
}
/**
* Returns the value of the Right/Left side in case the projection matches the side, else throw {@link NoSuchElementException}.
* That is:
* If this is a {@link RightProjection} with a {@link Right}
* or
* If this is a {@link LeftProjection} with a {@link Left}.
* Then return the value of the {@link Left}/{@link Right}.
* Any other case, throw {@link NoSuchElementException}.
*
* @return The value
*/
public T get() {
return asOption().get();
}
/**
* Returns the iterator of the Right/Left side in case the projection matches the side.
* That is:
* If this is a {@link RightProjection} with a {@link Right}
* or
* If this is a {@link LeftProjection} with a {@link Left}.
* Then return an iterator with the value for the {@link Left}/{@link Right}.
* Else return an empty iterator
*
* @return The iterator
*/
@Override
public Iterator iterator() {
return stream().iterator();
}
/**
* Returns the stream of the Right/Left side in case the projection matches the side.
* That is:
* If this is a {@link RightProjection} with a {@link Right}
* or
* If this is a {@link LeftProjection} with a {@link Left}.
* Then return a stream with the value for the {@link Left}/{@link Right}.
* Else return an empty stream
*
* @return The stream
*/
public Stream stream() {
return asOption().stream();
}
/**
* Returns the value of this projection if it is of the correct type else null.
* That is:
* If this is a {@link RightProjection} with a {@link Right}
* or
* If this is a {@link LeftProjection} with a {@link Left}.
* Then return the value of the {@link Left}/{@link Right}.
* Any other case, return null.
* In an essence this is a specialized version of {@link #getOrElse(Supplier)} where the supplier returns null.
* getOrElse(() -> null)
*
* @return The value or null
*/
public T orNull() {
return getOrElse(() -> null);
}
/**
* Returns the value of this projection if it is of the correct type else else the value provided by the supplier.
* That is:
* If this is a {@link RightProjection} with a {@link Right}
* or
* If this is a {@link LeftProjection} with a {@link Left}.
* Then return the value of the {@link Left}/{@link Right}.
* Any other case, return the value provided by the supplier.
*
* @param supplier
* The supplier to use if else becomes used
* @return The value or null
*/
public abstract T getOrElse(Supplier supplier);
}