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Split Maybe interface into MaybeOptional and MaybeStream

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Also deprecated Maybe.fromOptional(Optional)
This commit is contained in:
Paul Campbell 2018-06-22 23:52:29 +01:00
parent 24a12cbf5b
commit d6d17a6682
5 changed files with 143 additions and 64 deletions
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1
CHANGELOG
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@ -7,6 +7,7 @@ CHANGELOG
* Add `Result`
* Moved `Maybe` to `net.kemitix.mon.maybe.Maybe`
* Add `Maybe.stream()`
* Deprecate `Maybe.fromOptional(Optional)`
0.6.0
-----

69
src/main/java/net/kemitix/mon/maybe/Maybe.java
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@ -25,10 +25,6 @@ import lombok.NonNull;
import net.kemitix.mon.Functor;
import java.util.Optional;
import java.util.function.Consumer;
import java.util.function.Predicate;
import java.util.function.Supplier;
import java.util.stream.Stream;
/**
* A value that may or may not be present.
@ -37,7 +33,7 @@ import java.util.stream.Stream;
*
* @author Paul Campbell (pcampbell@kemitix.net)
*/
public interface Maybe<T> extends Functor<T, Maybe<?>> {
public interface Maybe<T> extends Functor<T, Maybe<?>>, MaybeStream<T>, MaybeOptional<T> {
/**
* Create a Maybe for the value that is present.
@ -85,69 +81,14 @@ public interface Maybe<T> extends Functor<T, Maybe<?>> {
* @param <T> the type of the Optional
*
* @return a Maybe
* @deprecated need to find a better way of converting an Optional to a Maybe, but
* without having to pass the Optional as a parameter
* Try: Optional.of(1).map(Maybe::just).orElseGet(Maybe::nothing)
*/
@Deprecated
static <T> Maybe<T> fromOptional(final Optional<T> optional) {
return optional.map(Maybe::maybe)
.orElse(nothing());
}
/**
* Provide a value to use when Maybe is Nothing.
*
* @param supplier supplier for an alternate value
*
* @return a Maybe
*/
T orElseGet(Supplier<T> supplier);
/**
* A value to use when Maybe is Nothing.
*
* @param otherValue an alternate value
*
* @return a Maybe
*/
T orElse(T otherValue);
/**
* Filter a Maybe by the predicate, replacing with Nothing when it fails.
*
* @param predicate the test
*
* @return the Maybe, or Nothing if the test returns false
*/
Maybe<T> filter(Predicate<T> predicate);
/**
* Convert the Maybe to an {@link Optional}.
*
* @return an Optional containing a value for a Just, or empty for a Nothing
*/
Optional<T> toOptional();
/**
* Provide the value within the Maybe, if it exists, to the Supplier, and returns the Maybe.
*
* @param consumer the Consumer to the value if present
*
* @return the Maybe
*/
Maybe<T> peek(Consumer<T> consumer);
/**
* Throw the exception if the Maybe is a Nothing.
*
* @param e the exception to throw
*
* @throws Exception if the Maybe is a Nothing
*/
@SuppressWarnings("illegalthrows")
void orElseThrow(Supplier<Exception> e) throws Exception;
/**
* Converts the Maybe into either a single value stream or and empty stream.
*
* @return a Stream containing the value or nothing.
*/
Stream<T> stream();
}

71
src/main/java/net/kemitix/mon/maybe/MaybeOptional.java Normal file
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@ -0,0 +1,71 @@
/**
* The MIT License (MIT)
*
* Copyright (c) 2017 Paul Campbell
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of this software
* and associated documentation files (the "Software"), to deal in the Software without restriction,
* including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all copies
* or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
* INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
* AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
package net.kemitix.mon.maybe;
import java.util.Optional;
import java.util.function.Supplier;
/**
* Enables emulation parts of and conversion to the Java Optional class for Maybe.
*
* @param <T> the type of the content of the Just
*
* @author Paul Campbell (pcampbell@kemitix.net)
*/
interface MaybeOptional<T> {
/**
* Provide a value to use when Maybe is Nothing.
*
* @param supplier supplier for an alternate value
*
* @return a Maybe
*/
T orElseGet(Supplier<T> supplier);
/**
* A value to use when Maybe is Nothing.
*
* @param otherValue an alternate value
*
* @return a Maybe
*/
T orElse(T otherValue);
/**
* Convert the Maybe to an {@link Optional}.
*
* @return an Optional containing a value for a Just, or empty for a Nothing
*/
Optional<T> toOptional();
/**
* Throw the exception if the Maybe is a Nothing.
*
* @param e the exception to throw
*
* @throws Exception if the Maybe is a Nothing
*/
@SuppressWarnings("illegalthrows")
void orElseThrow(Supplier<Exception> e) throws Exception;
}

62
src/main/java/net/kemitix/mon/maybe/MaybeStream.java Normal file
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@ -0,0 +1,62 @@
/**
* The MIT License (MIT)
*
* Copyright (c) 2017 Paul Campbell
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of this software
* and associated documentation files (the "Software"), to deal in the Software without restriction,
* including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all copies
* or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
* INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
* AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
package net.kemitix.mon.maybe;
import java.util.function.Consumer;
import java.util.function.Predicate;
import java.util.stream.Stream;
/**
* Enables emulation parts of and conversion to the Java Stream class for Maybe.
*
* @param <T> the type of the content of the Just
*
* @author Paul Campbell (pcampbell@kemitix.net)
*/
interface MaybeStream<T> {
/**
* Converts the Maybe into either a single value stream or and empty stream.
*
* @return a Stream containing the value or nothing.
*/
Stream<T> stream();
/**
* Filter a Maybe by the predicate, replacing with Nothing when it fails.
*
* @param predicate the test
*
* @return the Maybe, or Nothing if the test returns false
*/
Maybe<T> filter(Predicate<T> predicate);
/**
* Provide the value within the Maybe, if it exists, to the Supplier, and returns the Maybe.
*
* @param consumer the Consumer to the value if present
*
* @return the Maybe
*/
Maybe<T> peek(Consumer<T> consumer);
}

4
src/test/java/net/kemitix/mon/MaybeTest.java
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@ -85,8 +85,12 @@ public class MaybeTest implements WithAssertions {
@Test
public void fromOptional() {
// deprecated methods
assertThat(Maybe.fromOptional(Optional.of(1))).isEqualTo(just(1));
assertThat(Maybe.fromOptional(Optional.empty())).isEqualTo(nothing());
// recommended alternative
assertThat(Optional.of(1).map(Maybe::just).orElseGet(Maybe::nothing)).isEqualTo(just(1));
assertThat(Optional.empty().map(Maybe::just).orElseGet(Maybe::nothing)).isEqualTo(nothing());
}