两个集合的交集，并集，差

import java.util.*;

public class ListTest {
 public static void main(String[] args) {
  List<String> ls = new ArrayList<String>();
  List<String> ls2 = new ArrayList<String>();
  ls.add("George");
  ls.add("Jim");
  ls.add("John");
  ls.add("Blake");
  ls.add("Kevin");
  ls.add("Micheal");
  ls2.add("George");
  ls2.add("Katie");
  ls2.add("Micheal");
  ls2.add("Kevin");
  ls2.add("Ryan");
  System.out.println("第一个集合");// 打印输出第一个集合
  ListIterator lit0 = ls.listIterator();
  while (lit0.hasNext()) {
   System.out.print("  " + lit0.next());
  }
  System.out.println();
  System.out.println("第二个集合");// 打印输出第二个集合
  lit0 = ls2.listIterator();
  while (lit0.hasNext()) {
   System.out.print("  " + lit0.next());
  }
  System.out.println();

  jiao(ls, ls2);
  System.out.println();

  System.out.println("两个集合的并");
  lit0 = bing(ls, ls2).listIterator();
  while (lit0.hasNext()) {
   System.out.print("  " + lit0.next());
  }

  System.out.println();
  cha(ls, ls2);
 }

 public static void jiao(List ls, List ls2) {
  System.out.println("两个集合的交");
  List list = new ArrayList(Arrays.asList(new Object[ls.size()]));
  Collections.copy(list, ls);
  list.retainAll(ls2);
  Iterator lit0 = list.listIterator();
  while (lit0.hasNext()) {
   System.out.print("  " + lit0.next());
  }
 }

 public static List bing(List ls, List ls2) {
  List list = new ArrayList(Arrays.asList(new Object[ls.size()]));
  Collections.copy(list, ls);
  list.addAll(ls2);// 两个集合的并
  return list;
 }

 public static void cha(List ls, List ls2) {
  ls = bing(ls, ls2);
  List list = new ArrayList(Arrays.asList(new Object[ls.size()]));
  Collections.copy(list, ls);
  list.removeAll(ls2);// 两个集合的差

  System.out.println("两个集合的差");
  Iterator lit0 = list.listIterator();
  while (lit0.hasNext()) {
   System.out.print("  " + lit0.next());
  }
 }

}