集合Set、List、Map的遍历方法

 1 package com.shellway.javase; 2 import java.util.ArrayList; 3 import java.util.Collection; 4 import java.util.HashSet; 5 import java.util.Iterator; 6 import java.util.List; 7 import java.util.Map; 8 import java.util.Set; 9 import java.util.TreeMap;10 11 import org.junit.Test;12 13 public class TestCollection {14     15     public static void PRint(Collection<? extends Object> c){16         Iterator<? extends Object> it = c.iterator();17         while (it.hasNext()) {18             Object object = (Object) it.next();19             System.out.println(object);20         }21     }22     23     @Test24     public void demo1(){25         Set<String> set = new HashSet<String>();26         set.add("AAA");27         set.add("BBB");28         set.add("CCC");29         print(set);30         31         //Set的第一种遍历方式:利用Iterator32         Iterator<String> it1 = set.iterator();33         for (String ss : set) {34             System.out.println(ss);35         }36         //Set的第一种遍历方式:利用foreach37         for (String sss : set) {38             System.out.println(sss);39         }40         41         42         List<String> list = new ArrayList<String>();43         list.add("DDDDD");44         list.add("EEEEE");45         list.add("FFFFF");46         print(list);47         48         //List的第一种遍历方式:因为list有顺序，利用size()和get()方法获取49         for (int i = 0; i < list.size(); i++) {50             System.out.println(list.get(i));51         }52         //List的第二种遍历方式：利用Iterator53         Iterator<String> it = list.iterator();54         while (it.hasNext()) {55             System.out.println(it.next());56         }57         //List的第三种遍历方式:利用foreach58         for (String s2 : list) {59             System.out.println(s2);60         }61         62         63         Map<String,String> map = new TreeMap<String, String>();64         map.put("Jerry", "10000");65         map.put("shellway", "20000");66         map.put("Kizi", "30000");67         print(map.entrySet());68         //Map的第一种遍历方式：先获得key,再获得值value69         Set<String> sett = map.keySet();70         for (String s : sett) {71             System.out.println(s+":"+map.get(s));72         }73         //Map的第二种遍历方式：获得键值对74         for (Map.Entry<String, String> entry : map.entrySet()) {75             System.out.println(entry.getKey()+" : "+entry.getValue());76         }77     }78 }