返回两个集合的交集，而不修改原始集合。

//package com.nowjava;
/* 来自 n o w  j a v a  . c o m*/

import java.util.HashSet;


import java.util.Set;


public class Main {

    /**

     * Returns the intersection of two sets without modifying the original sets.<p>

     * 

     * @param <A> the type of objects contained in the sets

     * 

     * @param first the first set

     * @param second the second set

     * 

     * @return the intersection of both sets

     */

    public static <A> Set<A> intersection(Set<A> first, Set<A> second) {


        HashSet<A> result =