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https://github.com/ajoberstar/cljj
Clojure to Java Interop APIs
https://github.com/ajoberstar/cljj
clojure java
Last synced: 3 months ago
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Clojure to Java Interop APIs
- Host: GitHub
- URL: https://github.com/ajoberstar/cljj
- Owner: ajoberstar
- License: mit
- Created: 2015-07-29T01:23:11.000Z (over 9 years ago)
- Default Branch: main
- Last Pushed: 2022-08-13T20:17:04.000Z (over 2 years ago)
- Last Synced: 2024-09-16T17:42:39.960Z (5 months ago)
- Topics: clojure, java
- Language: Clojure
- Size: 203 KB
- Stars: 79
- Watchers: 7
- Forks: 4
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# cljj
[](http://clojars.org/org.ajoberstar/cljj)
[](https://cljdoc.org/d/org.ajoberstar/cljj)
**DISCLAIMER:** Prior to 0.5.0, this library was `org.ajoberstar/ike.cljj` with namespaces under `ike.cljj.*`. It is now `org.ajoberstar/cljj` with namespaces under `org.ajoberstar.cljj`.
## Why do you care?
Clojure provides some nice Java interop features, but they are missing clean support for newer APIs added to
Java 7+.
## What is it?
cljj is a Clojure library of wrappers around Java APIs.
### Current Support
* Clojure functions to arbitrary Single Abstract Method (SAM) types (`org.ajoberstar.cljj.function` -> `java.util.function` and others)
* Streams (`org.ajoberstar.cljj.stream` -> `java.util.stream`)
* NIO2 File API (`org.ajoberstar.cljj.file` -> `java.nio.file`)
## Usage
**NOTE:** cljj requires Java 8+
* [Release Notes](https://github.com/ajoberstar/cljj/releases)
### Reducing on a Stream
Requiring the `org.ajoberstar.cljj.stream` namespace will add support for two main things:
- Turning a Stream into an ISeq with `stream-seq`.
- Reducing/Transducing/etc over a Stream (due to `CollReduce` impl)
```clojure
(let [stream (IntStream/range 0 10)]
(= 25 (transduce (filter odd?) + stream))))
```
### Converting Clojure functions to Java SAMs
As of Java 8, there is powerful support in the Java language for lambdas and
method references. One of these features is that methods that accept an argument
which is a Single Abstract Method (SAM) interface can also accept any method reference
or lambda of the same shape/type.
This unforunately does not translate to Clojure users.
The `org.ajoberstar.cljj.function` namespace includes three main helpers for this:
* `sam*` - function converting a Clojure function to an arbitrary SAM interface
* `sam` - creating an anonymous SAM impl, as it were a Clojure function
* `defsam` - defining a named SAM impl, as if it were a Clojure function
**WARNING:** You may need type hints to avoid `IllegalAccessError` in Java 9+.
```clojure
(defsam my-sam
java.util.function.Predicate
[x]
(= x "it matched"))
;; ignore that I'm not using org.ajoberstar.cljj.stream here
(-> (Stream/of "not a match" "it matched")
(.filter my-sam)
(.collect Collectors/toList)
```
Note that primitive streams require different SAM types.
```clojure
;; ignore that I'm not using org.ajoberstar.cljj.stream here
(-> (IntStream/range 0 10)
(.filter (sam* java.util.function.IntPredicate odd?))
(.collect Collectors/toList)
```
### File API
The NIO2 API for files is much improved over `java.io.File`, but has some headaches from
Clojure, namely the extensive use of varargs. The `org.ajoberstar.cljj.file` namespace provides wrappers
over these functions for two benefits:
- more natural variadic functions for Clojure use (no explicit `into-array` calls)
- flexible argument types using the `Pathish` protocol that already converts many common types
to `Path` (e.g. `String`, `File`, `URI`).
## Questions, Bugs, and Features
Please use the repo's [issues](https://github.com/ajoberstar/cljj/issues)
for all questions, bug reports, and feature requests.
## Contributing
Contributions are very welcome and are accepted through pull requests.
Smaller changes can come directly as a PR, but larger or more complex
ones should be discussed in an issue first to flesh out the approach.
If you're interested in implementing a feature on the
[issues backlog](https://github.com/ajoberstar/cljj/issues), add a comment
to make sure it's not already in progress and for any needed discussion.