# Set operations : Set « Collections Data Structure « Java

Set operations

```

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
*
* @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) {
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) {
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) {
difference.removeAll(s2);
return difference;
}
}

```

### Related examples in the same category

 1 Set, HashSet and TreeSet 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