Eclipse Collections is a collections framework for Java. It has JDK-compatible List, Set and Map implementations with a rich API and set of utility classes that work with any JDK compatible Collections, Arrays, Maps or Strings. The iteration protocol was inspired by the Smalltalk collection framework.
Eclipse Collections puts iteration methods on the container types. Lambdas are simulated using anonymous inner classes. Here's a code example that demonstrates the usual style of programming with Eclipse Collections.
MutableList<Person> people = FastList.newListWith(person1, person2, person3);
MutableList<String> sortedLastNames = people.collect(Person.TO_LAST_NAME).sortThis();
System.out.println("Comma separated, sorted last names: " + sortedLastNames.makeString());Person.TO_LAST_NAME is defined as a constant Function in the Person class.
public static final Function<Person, String> TO_LAST_NAME = new Function<Person, String>()
{
public String valueOf(Person person)
{
return person.lastName;
}
};In Java 8, the Function can be replaced with a lambda:
MutableList<String> sortedLastNames = people.collect(person -> person.getLastName()).sortThis();Or, a method reference:
MutableList<String> sortedLastNames = people.collect(Person::getLastName).sortThis();- Improves readability and reduces duplication of iteration code (enforces DRY/OAOO)
- Implements several, high-level iteration patterns (select, reject, collect, inject into, etc.) on "humane" container interfaces which are extensions of the JDK interfaces
- Provides a consistent mechanism for iterating over Collections, Arrays, Maps, and Strings
- Provides replacements for ArrayList, HashSet, and HashMap optimized for performance and memory usage
- Performs more "behind-the-scene" optimizations in utility classes
- Encapsulates a lot of the structural complexity of parallel iteration and lazy evaluation
- Adds new containers including Bag, Interval, Multimap, BiMap, and immutable versions of all types
- Has been under active development since 2005 and is a mature library