java遍历Map的几种方法分析

Map<String,String> map=new HashMap<String,String>();map.put("username", "qq");map.put("passWord", "123");map.put("userID", "1");map.put("email", "qq@qq.com");

for(Map.Entry<String, String> entry:map.entrySet()){  System.out.println(entry.getKey()+"--->"+entry.getValue());}

Set set = map.entrySet();  Iterator i = set.iterator();  while(i.hasNext()){    Map.Entry<String, String> entry1=(Map.Entry<String, String>)i.next();    System.out.println(entry1.getKey()+"=="+entry1.getValue());}

Iterator it=map.keySet().iterator();while(it.hasNext()){  String key;  String value;  key=it.next().toString();  value=map.get(key);  System.out.println(key+"--"+value);}

Iterator it=map.entrySet().iterator();System.out.println( map.entrySet().size());String key;String value;while(it.hasNext()){  Map.Entry entry = (Map.Entry)it.next();  key=entry.getKey().toString();  value=entry.getValue().toString();  System.out.println(key+"===="+value);}