java Map & List 遍历

public static void main(String[] args) {


  Map<String, String> map = new HashMap<String, String>();
  map.put("1", "value1");
  map.put("2", "value2");
  map.put("3", "value3");
  
  //第一种：普遍使用，二次取值
  System.out.println("通过Map.keySet遍历key和value：");
  for (String key : map.keySet()) {
   System.out.println("key= "+ key + " and value= " + map.get(key));
  }
  
  //第二种
  System.out.println("通过Map.entrySet使用iterator遍历key和value：");
  Iterator<Map.Entry<String, String>> it = map.entrySet().iterator();
  while (it.hasNext()) {
   Map.Entry<String, String> entry = it.next();
   System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
  }
  
  //第三种：推荐，尤其是容量大时
  System.out.println("通过Map.entrySet遍历key和value");
  for (Map.Entry<String, String> entry : map.entrySet()) {
   System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
  }

  //第四种
  System.out.println("通过Map.values()遍历所有的value，但不能遍历key");
  for (String v : map.values()) {
   System.out.println("value= " + v);
  }
 }

package com.test;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
public class ArrayListDemo {
    public static void main(String args[]){
        List<String> list = new ArrayList<String>();
        list.add("luojiahui");
        list.add("luojiafeng");
        //方法1
        Iterator it1 = list.iterator();
        while(it1.hasNext()){
            System.out.println(it1.next());
        }
        //方法2
        for(Iterator it2 = list.iterator();it2.hasNext();){
             System.out.println(it2.next());
        }
        //方法3
        for(String tmp:list){
            System.out.println(tmp);
        }
        //方法4
        for(int i = 0;i < list.size(); i ++){
            System.out.println(list.get(i));
        }
    }
}