import java.util.Arrays;
import java.util.Collections;
import java.util.Set;
import java.util.TreeSet;

public class Sets {
    public static void main(String[] args){
        Set<Integer> a = new TreeSet<>();
        //TreeSet sorts on natural ordering (or an optional comparator)
        //other options: HashSet (hashcode)
        //               LinkedHashSet (insertion order)
        //               EnumSet (optimized for enum values)
        //others at: http://download.oracle.com/javase/7/docs/api/java/util/Set.html
        Set<Integer> b = new TreeSet<>();
        Set<Integer> c = new TreeSet<>();
        Set<Integer> d = new TreeSet<>();

        a.addAll(Arrays.asList(1, 2, 3, 4, 5));
        b.addAll(Arrays.asList(2, 3, 4, 5, 6, 8));
        c.addAll(Arrays.asList(2, 3, 4));
        d.addAll(Arrays.asList(2, 3, 4));
        System.out.println("a: " + a);
        System.out.println("b: " + b);
        System.out.println("c: " + c);
        System.out.println("d: " + d);

        System.out.println("2 in a: " + a.contains(2));
        System.out.println("6 in a: " + a.contains(6));

        Set<Integer> ab = new TreeSet<>();
        ab.addAll(a);
        ab.addAll(b);
        System.out.println("a union b: " + ab);

        Set<Integer> a_b = new TreeSet<>();
        a_b.addAll(a);
        a_b.removeAll(b);
        System.out.println("a - b: " + a_b);

        System.out.println("c subset of a: " + a.containsAll(c));
        //use a.conatins() for single elements

        System.out.println("c = d: " + c.equals(d));
        System.out.println("d = c: " + d.equals(c));

        Set<Integer> aib = new TreeSet<>();
        aib.addAll(a);
        aib.retainAll(b);
        System.out.println("a intersect b: " + aib);

        System.out.println("add 7 to a: " + a.add(7));
        System.out.println("add 2 to a again: " + a.add(2));

        //other noteworthy things related to sets:
        Set<Integer> empty = Collections.EMPTY_SET; //immutable empty set
        //empty.add(2);  would fail
        empty.isEmpty(); //test if a set is empty
        empty.size();
        Collections.disjoint(a, b); //returns true if the sets have no common elems (based on their .equals() methods)
        Collections.unmodifiableSet(a); //returns an immutable copy of a
    }
}