javascalautils.Some 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;
import static javascalautils.EitherCompanion.Right;
/**
* Represents an {@link Option} holding a value.
* The instance of {@link Some} is guaranteed to keep a non-null value object.
* Null values are not allowed as it implies an instance of {@link None}.
* One can consider {@link Some} as a collection of size 1.
*
* Either use the implementation directly:
*
*
*
* Option<String> option = new Some<>("Peter is Great!");
*
*
*
*
* or use the factory/apply method from Option:
*
*
*
* Option<String> option = Option.apply("Peter is Great!");
*
*
*
* For examples on usage refer to the documentation for {@link Option} .
*
* @author Peter Nerg
* @since 1.0
* @param The type of the value represented by this instance
*/
public final class Some extends SingleItemContainer implements Option, Serializable {
private static final long serialVersionUID = -17186529545151493L;
private final T value;
/**
* Creates an instance for the provided value.
* Null objects are not allowed and will render an exception.
*
* @param value The value represented by this Some
* @since 1.0
*/
public Some(T value) {
this.value = Validator.requireNonNull(value, "Null values are not allowed for Some");
}
/**
* Returns true if the predicate matches the value.
*
* @since 1.0
*/
@Override
public boolean exists(Predicate p) {
return p.test(value);
}
/**
* Always returns the value for this instance.
* Guaranteed to return a non-null value.
*
* @since 1.0
*/
@Override
public T get() {
return value;
}
/**
* Always returns the value for this instance.
*
* @since 1.0
*/
@Override
public T getOrElse(Supplier s) {
return value;
}
/**
* Returns an {@link Option} containing the value of applying the given function to the current
* value.
*
* @since 1.0
*/
@Override
public Option map(ThrowableFunction1 f) {
return flatMap(v -> Option.apply(f.apply(v)));
}
/**
* Returns an Option consisting of the result of applying the given function to the current value.
*
* @since 1.2
*/
@Override
public Option flatMap(ThrowableFunction1> function) {
try {
return function.apply(value);
} catch (Throwable ex) {
throw new BrokenFunctionException("Caught exception while applying function", ex);
}
}
/**
* Always returns this.
*
* @since 1.0
*/
@Override
public Option orElse(Supplier> s) {
return this;
}
/**
* Returns a {@link Left} containing the value of this instance.
*
* @since 1.4
*/
@Override
public Either toLeft(Supplier right) {
return Left(value);
}
/**
* Returns a {@link Right} containing the value of this instance.
*
* @since 1.4
*/
@Override
public Either toRight(Supplier left) {
return Right(value);
}
/**
* Returns true if the other object is {@link Some} containing a value that equals
* the value of this {@link Some}, else false.
*
* @since 1.0
*/
@Override
public boolean equals(Object other) {
// get is safe to invoke as it must be a Some and shall therefore always have a value
return (other instanceof Some) && ((Option) other).exists(o -> o.equals(value));
}
/**
* Returns the hashCode based on the value of this instance.
*
* @since 1.0
*/
@Override
public int hashCode() {
// no need for null checks on the value, as it per definition cannot be null
return 31 + value.hashCode();
}
/**
* Returns a String representation of the instance.
*
* @since 1.0
*/
@Override
public String toString() {
return String.format("Some(%s)", value);
}
}