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What this project provides:

  • The EnumBitSet is a data structure similar to EnumSet with more methods.
  • The EnumBitSetHelper interface allows to work directly on the enum constants.
  • The DomainBitSet is the interface implemented by EnumBitSet.

Set operations:

  • intersect
  • union
  • minus (relative complement)
  • complement
  • cross (Cartesian product)
  • semijoin (cross with filter)
  • powerset
  • map elements to different domain
  • zipWithPosition

Documentation:

All is documented and the ant build file contains a target "javadoc". Just run it, read the documentation directly in the source code, or read it online.

Java 8 and newer

Note that you can only use this with Java 8 and newer releases of Java.

Update to Java 10 in this branch:
https://github.com/claudemartin/enum-bit-set/tree/java10

Multi Paradigm

You can use the EnumBitSets like the EnumSets in Java. EnumBitSet is a mutable data structure with an interface you will recognize.

But it also supports a more functional approach, where a new set is returned for each operation. Use only those methods and the data structure can be used in a concurrent system. Those methods are thread-safe because they do not change any state.

Project website:

http://claude-martin.ch/enumbitset/

Example code:

// Examle enum type:
private static enum Permission implements EnumBitSetHelper<Permission> {
        READ, WRITE, EXECUTE, DELETE;
}

// Example code:

final EnumBitSet<Permission> permissions = bob.getPermissions();
// Add element to EnumBitSet:
permissions.add(Permission.READ);

// Check EnumBitSet:
if (Permission.WRITE.elementOf(permissions))
        Files.write(path, bytes);

// Functional Programming:

// Assume we have some users with permissions:
final List<User> users = getAllUsers();

// Get users with permission to DELETE:
final Stream<User> canDelete = users.stream().filter(u -> u.getPermissions().contains(Permission.DELETE));
// See what the group can do:
final Optional<EnumBitSet<Permission>> union = 
                canDelete.<EnumBitSet<Permission>> map(u -> u.getPermissions()).reduce(EnumBitSet<Permission>::union);
union.ifPresent(System.out::println); // [READ, WRITE, DELETE]

Note: If you think this code looks weird and not like Java then it's because Java 8 has new ways of working with Collections. This project provides a classic Java API and you can use conventional Java practices.

Outline of EnumBitSetHelper:

See the javadoc of EnumBitSetHelper to see what the interface offers.

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EnumSet and BitSet in one!

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