sample code to demonstrate HashSet class

package collection;

import java.util.HashSet;

public class HashSetDemo {
    public static void main(String arg[])
    {
    HashSet h=new HashSet();
    System.out.println(h.add("b")); // true
    h.add("b");
    h.add("c");
    h.add("d");
    h.add(null);
    h.add(new Integer(10));
    System.out.println(h.add("d")); // flase
    System.out.println(h); // depends on hash code number insertion order.
    }
}


output:
true
false
[d, null, c, 10, b]