關於HashSet Container

package container;
import java.util.Collection;
import java.util.HashSet;


public class Container {
    public static void main(String[] args) {
        Collection c = new HashSet();
        c.add("Hello");
        c.add(new Integer(100));
        c.add(new Name("Ming","li"));
        System.out.println(c);
        c.remove("Hello");
        System.out.println(c);
        c.remove(new Integer(100));
        System.out.println(c);
        c.remove(new Name("Ming","li"));    //不會移除對象，沒有重寫equals()無法判斷這個對象是否是c中已存在的對象。沒有重寫equals()時
        System.out.println(c);
        }
    }
    
class Name{
    private String firstname;
    private String lastname;
    public Name (String f,String l){
        firstname=f;
        lastname = l;
}
    public String toString (){
            return firstname+lastname;
    }

}