Result

Handle errors gracefully in a type-safe, functional manner similar to Kotlin's Result type or Scala's Try type using Java sealed classes.

A result is discriminated union that encapsulates a successful outcome with a value or a failure with an exception. Instances of Result<T> are either an instance of Success<T> or Failure<T>.

Using the library

Requires Java 17 (Java 21 is required to use pattern matching for switch or record patterns). View the API documentation.

To use the library add the https://maven.pkg.github.com/josephearl/result repository (see Using a published package for more information) and the dependency:

implementation 'io.github.josephearl.result:result:1.0.0-SNAPSHOT'

Example:

Result<Long> result =
    Result.of(() -> Files.readString(Path.of("example.txt")))
        .map((value) -> value.lines().count())
        .flatMap((value) -> Result.of(() -> 3L / value))
        .filter((value) -> value == 1L);

// Simple
long value = result.orElse(0L);

// Pattern matching for switch
long patternMatchValue =
    switch (result) {
      case Success<Long> success -> success.value();
      case Failure<Long> ignored -> 0L;
    };

// Pattern matching for switch with record patterns
long recordPatternMatchValue =
    switch (result) {
      case Success<Long>(var v) -> v;
      case Failure<Long>(var ignored) -> 0L;
    };

Developing the library

Requires Java 21. All commands are run from the root of the project, from a terminal:

Command	Action
./gradlew build	Build and run tests
./gradlew spotlessApply	Format code
./gradlew javadoc	Generate documentation
./gradlew publishToMavenLocal	Publish the library to your local Maven repository