java中HashMap的基本方法使用

package test;
import java.util.HashMap; 
import java.util.Iterator;   
import java.util.ArrayList;
import java.util.Collection;
import java.util.Map.Entry;
import java.util.Set;
public class test6 {

	public static void main(String[] args) {
		HashMap<String,Integer> map =new HashMap<>();
		map.put("a", 1);
		map.put("b", 2);
		map.put("c", 3);
		map.put("d", 4);
		
//		 Map map=new HashMap();                
//         map.put("a", "aaa");    
//         map.put("b", "bbb");    
//         map.put("c", "ccc");    
//         map.put("d", "ddd");    
		
		//hashMap遍历方法1
         Iterator<String> iterator = map.keySet().iterator();                
         while (iterator.hasNext()) {    
          Object key = iterator.next();    
          System.out.println("map.get(key) is :"+map.get(key));    
         }
         
         //遍历方法2
         Set<Map.Entry<String, Integer>> set=map.entrySet();
         Iterator<Map.Entry<String, Integer>> it=set.iterator();
         while(it.hasNext()){
       	  //System.out.println(list.get(0) );  
        	 Map.Entry<String, Integer> e=it.next();
       	  System.out.println(e.getKey()+":"+e.getValue());  
         }
         
          System.out.println(map.containsValue(1) );  
          System.out.println(map.containsKey("a") );  
          System.out.println(map.size() ); 
          System.out.println(map.remove("a") );  
          System.out.println(map.size() );  
          System.out.println(map.containsKey("a") );  
          System.out.println(map.containsValue(1) );  
          
          //ArrayList <Integer> list =(ArrayList<Integer>)map.values();      
          //上面会出现异常，因为map.values()返回的是一个Collection<Integer>对象，可用下面的方法解决
          ArrayList <Integer> list =new ArrayList<Integer>(map.values());    
          Iterator <Integer>ite=list.iterator();
          while(ite.hasNext()){
        	  //System.out.println(list.get(0) );  
        	  System.out.println(ite.next() );  
          }
          map.clear();
          System.out.println(map.isEmpty() );  
          
	}

}