java中遍历MAP的几种方法

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);

}