HashMap遍历 key value

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HashMap遍历的两种方式：  第一种:   
Map map = new HashMap();   
Iterator iter = map.entrySet().iterator();  
while (iter.hasNext()) {       
Map.Entry entry = (Map.Entry) iter.next();     
Object key = entry.getKey();      
Object val = entry.getValue();  
}
效率高,推荐使用此种方式！  
第二种:   
Map map = new HashMap();   
Iterator iter = map.keySet().iterator();  
while (iter.hasNext()) {       
Object key = iter.next();      
Object val = map.get(key);  }   
效率低比第一种要低，不推荐使用！
public class HashMapTest {          
public static void main(String[] args) {           
HashMap hashmap = new HashMap();            
for (int i = 0; i < 1000; i++ ){             
hashmap.put(i, "thanks");            
}              
long bs = Calendar.getInstance().getTimeInMillis();            
Iterator iterator = hashmap.keySet().iterator();               
while (iterator.hasNext()){                 
System.out.print(hashmap.get(iterator.next()));            
}             
System.out.println();             
System.out.println(Calendar.getInstance().getTimeInMillis() - bs);               
listHashMap();          
}                    
public static void listHashMap(){                     
java.util.HashMap hashmap = new java.util.HashMap();                    
for (int i = 0; i < 1000; i++ ){                     
hashmap.put(i, "thanks");                    
}                     
long bs = Calendar.getInstance().getTimeInMillis();                      
java.util.Iterator it = hashmap.entrySet().iterator();                    
while (it.hasNext()){                      
java.util.Map.Entry entry = (java.util.Map.Entry) it.next();// entry.getKey() 返回与此项对应的键                     
// entry.getValue() 返回与此项对应的值                     
System.out.print(entry.getValue());                    
}                     
System.out.println();                    
System.out.println(Calendar.getInstance().getTimeInMillis() - bs);                 
}  }

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