# Set operations : Set « Collections Data Structure « Java

- Java
- Collections Data Structure
- Set

Set operations

**import** java.util.LinkedHashSet;
**import** java.util.Set;
/**
* Note: This code is based on -<br>
* http://java.sun.com/docs/books/tutorial/collections/interfaces/set.html<br>
*
* Using LinkedHashSet, even though slightly slower than HashSet, in order to
* ensure order is always respected (i.e. if called with TreeSet or
* LinkedHashSet implementations).
*
* @author Ravi Mohan
* @author Ciaran O'Reilly
*/
**public** **class** SetOps {
/**
*
* @param <T>
* @param s1
* @param s2
* @return the union of s1 and s2. (The union of two sets is the set
* containing all of the elements contained in either set.)
*/
**public** **static** <T> Set<T> union(Set<T> s1, Set<T> s2) {
Set<T> union = **new** LinkedHashSet<T>(s1);
union.addAll(s2);
**return** union;
}
/**
*
* @param <T>
* @param s1
* @param s2
* @return the intersection of s1 and s2. (The intersection of two sets is
* the set containing only the elements common to both sets.)
*/
**public** **static** <T> Set<T> intersection(Set<T> s1, Set<T> s2) {
Set<T> intersection = **new** LinkedHashSet<T>(s1);
intersection.retainAll(s2);
**return** intersection;
}
/**
*
* @param <T>
* @param s1
* @param s2
* @return the (asymmetric) set difference of s1 and s2. (For example, the
* set difference of s1 minus s2 is the set containing all of the
* elements found in s1 but not in s2.)
*/
**public** **static** <T> Set<T> difference(Set<T> s1, Set<T> s2) {
Set<T> difference = **new** LinkedHashSet<T>(s1);
difference.removeAll(s2);
**return** difference;
}
}

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2. | Things you can do with Sets | | |

3. | Set operations: union, intersection, difference, symmetric difference, is subset, is superset | | |

4. | Set implementation that use == instead of equals() | | |

5. | Set that compares object by identity rather than equality | | |

6. | Set union and intersection | | |

7. | Set with values iterated in insertion order. | | |

8. | Putting your own type in a Set | | |

9. | Use set | | |

10. | Another Set demo | | |

11. | Set subtraction | | |

12. | Working with HashSet and TreeSet | | |

13. | TreeSet Demo | | |

14. | Show the union and intersection of two sets | | |

15. | Demonstrate the Set interface | | |

16. | Array Set extends AbstractSet | | |

17. | Sync Test | | |

18. | Set Copy | | |

19. | Set and TreeSet | | |

20. | Tail | | |

21. | What you can do with a TreeSet | | |

22. | Remove all elements from a set | | |

23. | Copy all the elements from set2 to set1 (set1 += set2), set1 becomes the union of set1 and set2 | | |

24. | Remove all the elements in set1 from set2 (set1 -= set2), set1 becomes the asymmetric difference of set1 and set2 | | |

25. | Get the intersection of set1 and set2, set1 becomes the intersection of set1 and set2 | | |

26. | Extend AbstractSet to Create Simple Set | | |

27. | Int Set | | |

28. | One Item Set | | |

29. | Small sets whose elements are known to be unique by construction | | |

30. | List Set implements Set | | |

31. | Converts a char array to a Set | | |

32. | Converts a string to a Set | | |

33. | Implements the Set interface, backed by a ConcurrentHashMap instance | | |

34. | An IdentitySet that uses reference-equality instead of object-equality | | |

35. | An implementation of the java.util.Stack based on an ArrayList instead of a Vector, so it is not synchronized to protect against multi-threaded access. | | |

36. | A thin wrapper around a List transforming it into a modifiable Set. | | |

37. | A thread-safe Set that manages canonical objects | | |

38. | This program uses a set to print all unique words in System.in | | |

39. | Indexed Set | | |

40. | An ObjectToSet provides a java.util.Map from arbitrary objects to objects of class java.util.Set. | | |

41. | Sorted Multi Set | | |

42. | Fixed Size Sorted Set | | |

43. | A NumberedSet is a generic container of Objects where each element is identified by an integer id. | | |

44. | Set which counts the number of times a values are added to it. | | |

45. | Set which counts the number of times a values are added to it and assigns them a unique positive index. | | |

46. | Indexed Set | | |

47. | A set acts like array. | | |

48. | Implements a Bloom filter. Which, as you may not know, is a space-efficient structure for storing a set. | | |

49. | Implementation of disjoint-set data structure | | |

50. | Call it an unordered list or a multiset, this collection is defined by oxymorons | | |