双向迭代器

 1 package testBlog;
 2 
 3 import java.util.ArrayList;
 4 import java.util.Collection;
 5 import java.util.HashSet;
 6 import java.util.Iterator;
 7 import java.util.List;
 8 import java.util.ListIterator;
 9 import java.util.Set;
10 import java.util.TreeSet;
11 
12 public class Test {
13     public static void main(String[] args) {
14         List<String> all = new ArrayList<>();
15         all.add("abcdef");
16         all.add("abcde");
17         all.add("abcd");
18         all.add("abc");
19         
20         ListIterator<String> iter = all.listIterator();//双向迭代器
21         
22         System.out.println("由前向后输出");
23         while(iter.hasNext()) {
24             String str = iter.next();
25             System.out.println(str+",");
26         }
27         
28         System.out.println("由后向前输出");
29         while(iter.hasPrevious()) {
30             String str = iter.previous();
31             System.out.println(str+",");
32         }
33 
34     }
35 }
结果:
由前向后输出
abcdef,
abcde,
abcd,
abc,
由后向前输出
abc,
abcd,
abcde,
abcdef,