Collection of classes that makes functional programming easier in Java prior to version 8.
Functional programming is a very effective methodology that helps to create more readable code built from better reusable code fragments. Java supports functional programming since version 8. Although Java 8 was released on June, 2014 there are still poor people that have to write code compatible with previous versions.
It is not a nightmare however. There are several frameworks that bring functional programming to Java 7 and earlier:
- Guava
- Apache collections framework (v3 and v4)
- Apache commons functor (not yet officially released project)
- Functional java
These libraries help us to create functional code but still require to implement again and again the same (often trivial) code fragments.
For example, let's say I want to filter given strings collections so that only strings that starts with "a" remain.
Using Guava I have to define startsWith predicate like the following:
Iterable<String> filtered = FluentIterable.from((Set<String>) page).filter(new Predicate<String>() {
@Override
public boolean apply(String input) {
return input.startsWith("a");
}
});Not bad, but I'd like to avoid writing such trivial functions every time I need them. I'd prefer to have collection of ready to use functions and predicates that hopefully cover more than 50% of my needs. I'd like to be able to re-write the code above as following:
Iterable<String> filtered = FluentIterable.from((Set<String>) page).filter(startsWith("a"));(obviously I have to add static import to get access to reusable function startsWith().)
So, this is exactly what this library does. The library implements general functions and predicates that can be used as a building blocks within several functional frameworks. Right now the FuncKit supports
- Guava
- Apache collections v3
- Apache collections v4
// Get recursively tree of existing properties files older than 1 hour starting from current directory and load their content into single Properties object
Properties props = new Properties();
FluentIterable
.from(asList(tree(matchesWildcard("*.properties")).apply(new File("."))))
.filter(and(isFile, exists)).filter(checkField(lastModified, gt(3600000L)))
.transform(fis)
.transform(load(props));FuncKit is not deployed to any public maven repository yet. But once this is done you will have to include 2 dependencies in order to use it.
First you need dependency to FuncKit core that contains most of the code.
<dependency>
<groupId>org.funckit</groupId>
<artifactId>funckit-core</artifactId>
<version>0.1-SNAPSHOT</version>
</dependency>Second you have to include one of the following dependencies according to the functional framework you are using:
funckit-guava-basefunckit-commons-collections-basefunckit-commons-collections4-base
e.g:
<dependency>
<groupId>org.funckit</groupId>
<artifactId></artifactId>
<version>0.1-SNAPSHOT</version>
</dependency>At the moment the library cannot be used with 2 functional frameworks in the same project. This limitation however will be fixed before the first release.
Curious reader that wants to know the reason for this limitation should read chapter "Design".
TBD
TBD