list集合，map集合遍历

 

import java.util.ArrayList;   
import java.util.Iterator;   
import java.util.List;   
  
/**  
*遍历集合List  
 * @author Men、叔 
*  Email 844357411@qq.com  【Men 叔 Java厂】：http://jq.qq.com/?_wv=1027&k=cfqLhZ
 */  
public class Demo {   
  
    /**  
     * @param args  
     */  
    public static void main(String[] args) {   
       
        List list = new ArrayList();   
        list.add("aaa");   
       list.add("bbb");   
        //1:利用下标   
     for(int i = 0 ; i< list.size();i++){   
               
            System.out.println(list.get(i));   
       }   
        //2:for- each   
        for(Object o:list){   
          System.out.println(o);   
        }   
        //3:迭代器   
       Iterator it = list.iterator();   
       while(it.hasNext()){   
          System.out.println(it.next());   
        }   
       //4:Object数组    
      Object o[];   
        o = list.toArray();   
        for(int i =  0 ; i <o.length;i++){   
        System.out.println(o[i]);   
       }   
       //5:toString   
       System.out.println(list.toString());   
  
    }   
  
}  
public class Demo{
public static void main(String[] args) {


  Map<String, String> map = new HashMap<String, String>();
  map.put("1", "value1");
  map.put("2", "value2");54   
  //1：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));
  }
  
  //2:迭代器遍历
  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());
  }
  
  //3：foreach 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());
  }

  //4
  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);
  }
 }
}