# fold-java

**Repository Path**: mirrors_andyglick/fold-java

## Basic Information

- **Project Name**: fold-java
- **Description**: Fold operator
- **Primary Language**: Unknown
- **License**: MIT
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2020-09-24
- **Last Updated**: 2026-02-28

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# left fold [![Build Status](https://travis-ci.org/daggerok/fold-java.svg?branch=master)](https://travis-ci.org/daggerok/fold-java)
Kotlin to the rescue
<!--I don't know why, but people so confused about that simple operation...-->

_DomainEvents.kt_

```kotlin
@file:JvmName("DomainEvents")

interface DomainEvent {
  val type: Class<out DomainEvent>
    get() = this.javaClass
}

class CounterCreatedEvent : DomainEvent
class CounterIncrementedEvent : DomainEvent
class CounterDecrementedEvent : DomainEvent

fun Aggregate.apply(event: DomainEvent): Aggregate = when (event) {
  is CounterCreatedEvent -> this.on(event)
  is CounterIncrementedEvent -> this.on(event)
  is CounterDecrementedEvent -> this.on(event)
  else -> throw IllegalStateException("unexpected unsupported domain event occur: $event")
}
```

_Some.java_

```java
Optional<Aggregate> foldLeft(Aggregate initialState, DomainEvent... events) {
  if (events.length <= 0) return Optional.empty();
  Aggregate accumulator = initialState;
  for (DomainEvent event : events)
    accumulator = DomainEvents.apply(accumulator, event);
  return Optional.of(accumulator);
}
```


group:

- [lazy-java](https://github.com/daggerok/lazy-java)
- [java-examples](https://github.com/daggerok/java-examples)
- [learn-jvm](https://github.com/daggerok/learn-jvm)
- [fold-java](https://github.com/daggerok/fold-java)