Motif

A pattern matching library for Java 8. Motif provides scala-like pattern matching in Java 8.

Examples

FizzBuzz

IntStream.range(0, 101).forEach(
    n -> System.out.println(
        match(Tuple2.of(n % 3, n % 5))
            .when(tuple2(eq(0), eq(0))).get(() -> "FizzBuzz")
            .when(tuple2(eq(0), any())).get(y -> "Fizz")
            .when(tuple2(any(), eq(0))).get(x -> "Buzz")
            .orElse(String.valueOf(n))
            .getMatch()
    )
);

Optional

Optional<Person> personOpt = getPerson();
match(personOpt)
    .when(some(any())).then(person -> doStuff(person))
    .when(none()).then(() -> System.out.println("Person not found"))
    .doMatch();

Factorial

public long factorial(long i) {
  return match(i)
      .when(eq(0)).get(() -> 1l)
      .when(any()).get(x -> x * factorial(x - 1))
      .getMatch();
}

Nested Matching

Optional<Tuple2<String, String>> opt = Optional.of(Tuple2.of("first", "second"));
match(opt)
    .when(some(tuple2(eq("third"), any()))).then(b -> doStuff(b))
    .when(some(tuple2(any(), eq("second")))).then(a -> doStuff(a))
    .when(none()).then(() -> System.out.println("Tuple not found"))
    .doMatch();

List Cons Matching

List<String> list = Arrays.asList("a", "b", "c", "d");
match(list)
    .when(nil()).then(() -> System.out.println("Empty List"))
    .when(headNil(eq("b"))).then(() -> System.out.println("Singleton List of 'b'"))
    .when(headNil(any())).then(head -> System.out.println("Singleton List of " + head))
    .when(headTail(any(), any())).then(
        (head, tail) -> System.out.println("head: " + head + " Remaining: " + tail))
    .doMatch();

Download

Download the latest JAR via Maven:

<dependency>
  <groupId>com.leacox.motif</groupId>
  <artifactId>motif</artifactId>
  <version>0.1</version>
</dependency>

License

Copyright 2015 John Leacox

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.