fluent-lambda

A concise and declarative way to define lambda expressions in Java. It builds on top of Guava and provides an alternative to anonymous inner classes for defining Functions and Predicates when those functors just wrap single object-level method invocations.

Examples

These examples are completely fleshed out in the unit tests.

Defining Predicates.

Let's say you have a collection of matrices and you want to retain only the ones that are square. Guava makes this easy:

com.google.common.collect.Collections2.filter(matrices, matrixIsSquare);

Typically the matrixIsSquare Predicate would be defined like this:

Predicate<AnyMatrix> matrixIsSquare = new Predicate<AnyMatrix>() {
    public boolean apply(AnyMatrix input) {
        return input.isSquare();
    }
};

It seems excessive for just a simple method invocation. fluent-lambda provides a concise and declarative way of defining the same Predicate:

Predicate<AnyMatrix> matrixIsSquare = forMethod(ofClass(AnyMatrix.class).isSquare());

It uses an example method invocation to define the Predicate. There is no need for referencing classes or methods by name, so it is refactoring-friendly.

Defining Functions

Let's say you have a collection of vectors that you would like to get the norms of those vectors. Again, Guava makes this easy:

com.google.common.collect.Lists.transform(vectors, normCalculator);

Typically, the normCalculator Function would be defined like this:

Function<RealVector, Double> normCalculator = new Function<RealVector, Double>() {
    public Double apply(RealVector input) {
        return input.getNorm();
    }
};

This also seems excessive for just a simple method invocation. fluent-lambda provides a concise and declarative way of defining Functions as well:

Function<RealVector, Double> normCalculator = forMethod(ofClass(RealVector.class).getNorm());

Getting the Library

fluent-lambda is available in The Central Repository.

Maven

To include the library in your Maven project, add the following dependency to your POM:

<dependency>
  <groupId>com.macasaet.lambda</groupId>
  <artifactId>fluent-lambda</artifactId>
  <version>0.2.1</version>
</dependency>

Gradle

To include the library in your Gradle project, add the following dependency to build.gradle:

compile group: 'com.macasaet.lambda', name: 'fluent-lambda', version: '0.1.2'

Manual

You can download the library directly from The Central Repository.

Building the Project

fluent-lambda uses the Gradle build system. To build from the command line, type:

./gradlew install

Known Issues

fluent-lambda currently does not build with JDK 6.

Continuous Integration

Releasing Deployments to the Central Repository

Before releasing to Central, you will need to define the following properties in your build.gradle file:

signing.keyId=[your eight-character public key ID]
signing.secretKeyRingFile=[full path to the secret key ring that contains the keyId]
nexusUsername=[your username for Central]

To build and release to Central, type:

./gradlew --no-daemon uploadArchives

You will be prompted for the password to your secret key and for your Central password.