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# lemonad
_Some functional sweetness for Java._
This library provides useful monads that are not present in the JDK.
The defined types and API are minimal and highly composable with the standard ones, avoiding re-inventing them.
## Usage
The Javadoc for the latest snapshot version is available online [here][javadoc].
[javadoc]: https://javadoc.jitpack.io/org/pacien/lemonad/master-SNAPSHOT/javadoc/
### Attempt
The `Attempt` monad represents a computation which can be either successful or failed.
It allows the transformation of results and the recovery of errors in a pipeline,
similarly to [Scala's `Try`][scala-try] or [Java's `CompletableFuture`][java-completable-future].
This monad does __not__ require the error type to be a `Throwable`,
the use of which being problematic in performance-sensitive contexts.
[scala-try]: https://www.scala-lang.org/api/2.12.8/scala/util/Try.html
[java-completable-future]: https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/concurrent/CompletableFuture.html
```java
import static org.pacien.lemonad.attempt.Attempt.*;
(tree.hasLemon() ? success(tree.getLemon()) : failure("No lemon."))
.recoverError(__ -> store.buyLemon())
.transformResult(this::makeLemonade)
.ifSuccess(this::drink);
```
### Validation
The `Validation` monad represents a validation of a subject which can be either valid or invalid.
In the latter case, the monad wraps one or multiple validation errors in addition to the subject of the validation.
The `Validator` functional interface represents a function which performs verification operations on a supplied subject and returns
a `Validation`.
`Validator`s can be composed to perform verifications against multiple criteria and obtain an aggregated `Validation`.
```java
import static org.pacien.lemonad.validation.Validator.*;
var validator = validatingAll(
ensuringPredicate(not(Lemon::isRotten), "Bad lemon."),
validatingField(Lemon::juiceContent, ensuringPredicate(mL -> mL >= 40, "Not juicy.")));
validator.validate(lemon)
.ifValid(this::makeLemonade)
.ifInvalid(errors -> makeLifeTakeTheLemonBack());
```
## Setup
_lemonad_ requires Java 11 or above.
Binaries are compiled by and distributed through [JitPack][jitpack-page].
[jitpack-page]: https://jitpack.io/#org.pacien/lemonad
### Gradle (`build.gradle`)
```groovy
repositories {
maven { url 'https://jitpack.io' }
}
dependencies {
implementation 'org.pacien:lemonad:60a6659264'
}
```
### Maven (`pom.xml`)
```xml
<project>
<repositories>
<repository>
<id>jitpack.io</id>
<url>https://jitpack.io</url>
</repository>
</repositories>
<dependency>
<groupId>org.pacien</groupId>
<artifactId>lemonad</artifactId>
<version>60a6659264</version>
</dependency>
</project>
```
## License
Copyright (C) 2019 Pacien TRAN-GIRARD.
_lemonad_ is distributed under the terms of GNU Affero General Public License v3.0, as detailed in the attached `license.md` file.
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