readme.md

A Result Type for the Rest of Us

This package contains a small, composable Result type heavily inspired by Rust. It provides ergonomic and robust error handling and leverages Java's type system to make uncaught runtime exceptions a thing of the past.

Installation

This package can be found on Maven Central. For POM files, add the following:

<dependency>
  <groupId>dev.kylesilver</groupId>
  <artifactId>result-type-jvm</artifactId>
  <version>0.1.2</version>
</dependency>

For Gradle projects, use:

implementation 'dev.kylesilver:result-type-jvm:0.1.2'

Usage

A Result type indicates that a value is either a success Ok or an error Err. Before accessing the value inside, you must inspect the Result to determine which of the two possible outcomes have occurred.

Instead of throwing an exception, you can return an error value.

// indicates the value was successful
Result<Integer, String> ok = Result.ok(1);

// indicates there was an error
Result<Integer, String> err = Result.err("something went wrong!");

If you want to get the value out and throw an exception if there's an error, you can do so with unwrap()

int value = result.unwrap();

You can also substitute a default value in the event of an error

int value = result.err().orElse(0);

And you can also apply stream-style maps which are only applied to the value if it is Ok

// the map is applied to Ok values
Result<Integer, String> result1 = Result.ok(5);
String result = result1.map(x -> Integer.toString(x)).unwrap();

// but not to errors
Result<Integer, String> result2 = Result.err("whoops!");
result2.map(x -> Integer.toString(x)).isErr(); // true

You can use match to apply more complex manipulations to the result of an operation.

Result<Integer, String> result = Result.ok(5);
int computed = result.match(
    ok -> ok + 1,
    err -> {
        log.warn("there was an error!");
        return 0;
    }
);

There's a lot more that you can do with Result types, check out the docs for more details.