Iterator

 

 

	public static void main(String[] args) {
		Map<String, Integer> hashmap = new HashMap<String, Integer>();
		long e = System.currentTimeMillis();
//		for (int i = 0; i < 1000000; i++) {
//			hashmap.put(i,"bsdfsewfasdfasf"+i);
//		}
		hashmap.put("cc",1);
		hashmap.put("aa",2);
		hashmap.put("bb",3);
		long a = System.currentTimeMillis();
		System.out.println(a-e);
		Iterator iter = hashmap.entrySet().iterator();       
		while(iter.hasNext()) {   
		    Map.Entry entry = (Map.Entry)iter.next();   
		    String key = (String) entry.getKey();   
		    Integer value = (Integer) entry.getValue();
		    System.out.println(key + " " + value);
		}  
		long b = System.currentTimeMillis();
		System.out.println(b-a);
		long c = System.currentTimeMillis();
		for(Iterator iterator = hashmap.keySet().iterator(); iterator.hasNext();)
		{
			String key = (String)iterator.next();
			Integer value = (Integer)hashmap.get(key);
			System.out.println(key + " " + value);
		}
		long d = System.currentTimeMillis();
		System.out.println(d-c);
	}

打印结果

aa 2
bb 3
cc 1

 

 

有啥玄机？？？？