There’s no built in type for ConcurrentHashSet because you can always derive a set from a map. Since there are many types of maps, you use a method to produce a set from a given map (or map class). Prior to Java 8, you produce a concurrent hash set backed by a concurrent hash map, … Read more
Use the retainAll() method of Set: Set<String> s1; Set<String> s2; s1.retainAll(s2); // s1 now contains only elements in both sets If you want to preserve the sets, create a new set to hold the intersection: Set<String> intersection = new HashSet<String>(s1); // use the copy constructor intersection.retainAll(s2); The javadoc of retainAll() says it’s exactly what you … Read more
HashSet is much faster than TreeSet (constant-time versus log-time for most operations like add, remove and contains) but offers no ordering guarantees like TreeSet. HashSet the class offers constant time performance for the basic operations (add, remove, contains and size). it does not guarantee that the order of elements will remain constant over time iteration … Read more