Lambda

Staccatissimo-Lambda

Quick Overview

Staccatissimo-Lambda is a minimalistic and lightweight library for instantiating simple Staccatissimo-Defs' Functions and Predicates in a DSL style, without using anonymous classes. This project is aimed to simplify higher-order programming within Staccatissimo until Java adds lambdas to its language (planned for Java 8)

Getting Started

The entry point to Staccatissimo-Lambda is the Lambda class, which allows to create functions in a concise and redable way. There are two ways of using it, this introduction will just show one of them - using a shared lambda factory. The alternative, more performant but a bit more verbose way - using local lambda factories - is discussed in the API docs.

Instantiating 1 argument functions

The simplest function to create are one argument functions. Without Staccatissimo-Lambda, implementing such functions require to extend AbstractFunction. For example, a function that return book's ISBN looks like the following:

  import net.sf.staccatocommons.lang.function.AbstractFunction; 
  ...
  new AbstractFunction<Book, String>() {
    public String apply(@NonNull Book book){
        return book.getIsbn();
    }  
  };  

Which is OK, but is far from being the panacea. In particular, it is not too readable. This can be improved statically importing Lambda:

  import static net.sf.staccatocommons.lambda.*;
  ...
  lambda($(Book.class).getIsbn()); 

Which, although is odd at first glance, is much more intention revealing.

Functions that can be instantiated using this syntax are not restricted to getters, for example:

  lambda($(List.class).size());  
  lambda($(List.class).contains("hello"));
  lambda($(List.class).get(2));

Instantiating 2 and 3 arguments functions

Creating instances of Function2 and Function3 is also quite simple. For example, the following code:

  new AbstractFunction2<Book, WeightUnit, BigDecimal>(){
   public BigDecimal apply(Book book, WeightUnit unit) {
     return book.getWeigth(unit);
   }
  };

can be rewritten using lambdas:

  lambda2($(Book.class).getWeight(_(WeightUnit.class));

Learn More

Check Javadoc:

• Lambda
• Staccatissimo-Defs functions
• Staccatissimo-Lang abstract functions
• Staccatissimo-Defs predicates
• Staccatissimo-Lang abstract predicates

Adding it to your project

Add it as a Maven dependency

    <dependencies>
        <dependency>
            <groupId>net.sf.staccatocommons</groupId>
            <artifactId>staccatissimo-lambda</artifactId>
            <version>${staccatissimo.version}</version>
        </dependency>
    </dependencies>