set接口

        Set s1=new HashSet();
        Set s2=new HashSet();
        s1.add("a");
        s1.add("b");
        s1.add("c");
        s2.add("d");
        s2.add("a");
        s2.add("b");
        Set sn=new HashSet(s1);
        sn.retainAll(s2);
        Set su=new HashSet(s1);
        su.addAll(s2);
        System.out.println(sn);
        System.out.println(su);

import java.util.*;

class Name
{
    private String firstName,lastName;
    
    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    public Name(String firstName,String lastName)
    {
        this.firstName=firstName;
        this.lastName=lastName;        
    }
    public boolean equals(Object obj)
    {
        if (obj instanceof Name)
        {
            Name name=(Name)obj;
            return (firstName.equals(name.firstName)) && (lastName.equals(name.lastName));            
        }
        
        return super.equals(obj);
    }
    public int hashCode()
    {
        return firstName.hashCode();
    }
    public String toString() {  return firstName + " " + lastName;  }    
    
}



public class testmy1 {
    
    public static void main(String[] args) 
    {
        Set s=new HashSet();
        s.add("hello");
        s.add("world");
        s.add(new Name("f1","f2"));
        s.add(new Integer(100));
        s.add(new Name("f1","f2"));
        s.add("hello");
        System.out.println(s);
    }

}