循环遍历Map的几种方式

Map<String,String> map=new HashMap<String,String>();
map.put("username", "qq");
map.put("passWord", "123");
map.put("userID", "1");
map.put("email", "[e-mail]");

第一种用for循环

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

第二种用迭代

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());
}

用keySet()迭代

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);
}

用entrySet()迭代

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);                 
}