javascalautils.LeftProjection 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.io.Serializable;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.Supplier;
import static javascalautils.EitherCompanion.Left;
/**
* This is a left-biased wrapper for an instance of {@link Either}.
*
* @author Peter Nerg
* @since 1.1
*/
public class LeftProjection extends Projection implements Iterable, Serializable {
private static final long serialVersionUID = 4251047373391313192L;
private final Either either;
/**
* Creates an instance of the projection.
*
* @param either The instance to wrap.
* @since 1.1
*/
LeftProjection(Either either) {
this.either = either;
}
/**
* Returns false if {@link Right} or returns the result of applying the predicate to
* the {@link Left} value.
*
* @param predicate The predicate to apply
* @return If this is a {@link Left} and the predicate matches the value
* @since 1.1
*/
public boolean exists(Predicate predicate) {
return either.isLeft() && predicate.test(orNull());
}
/**
* Returns the value if this is a {@link Left} else the value provided by the supplier.
*
* @param supplier The supplier
* @return The value
* @since 1.1
*/
@Override
public L getOrElse(Supplier supplier) {
return either.fold(v -> v, v -> supplier.get());
}
/**
* Returns a {@link Some} wrapping the {@link Either} if it's a {@link Left} and the value of the
* {@link Left} matches the predicate, else {@link None} .
*
* @param predicate The predicate to apply
* @return The resulting Option of the filter operation
* @since 1.1
*/
public Option> filter(Predicate predicate) {
return Option.apply(exists(predicate) ? either : null);
}
/**
* Returns true if {@link Right} or returns the result of applying the predicate to
* the {@link Left} value.
*
* @param predicate The predicate to apply
* @return If it is a match
* @since 1.1
*/
public boolean forAll(Predicate predicate) {
return !either.isLeft() || predicate.test(orNull());
}
/**
* If this projection contains a {@link Left} then a new {@link Left} is returned containing the
* value from the original {@link Right} mapped via the provided function, else the contained
* Either is returned as is.
*
* @param The type to return as the new {@link Left}
* @param function The function
* @return Mapped Either
* @since 1.1
*/
@SuppressWarnings("unchecked")
public Either map(Function function) {
return either.isLeft() ? Left(function.apply(get())) : (Either) either;
}
/**
* If this projection contains a {@link Left} then a new {@link Left} is returned containing the
* value from the original {@link Right} mapped via the provided function, else the contained
* Either is returned as is.
*
* @param The type to return as the new {@link Left}
* @param function The function
* @return Mapped Either
* @since 1.2
*/
@SuppressWarnings("unchecked")
public Either flatMap(Function> function) {
return either.isLeft() ? function.apply(get()) : (Either) either;
}
}