map的几种迭代

Java代码
Map map=new HashMap();
map.put("username", "qq");
map.put("passWord", "123");
map.put("userID", "1");
map.put("email", "[email protected]");
第一种用for循环
Java代码
for(Map.Entry entry:map.entrySet()){
    System.out.println(entry.getKey()+"--->"+entry.getValue());
}
第二种用迭代
Java代码
Set set = map.entrySet();   
Iterator i = set.iterator();   
while(i.hasNext()){
    Map.Entry entry1=(Map.Entry)i.next();
    System.out.println(entry1.getKey()+"=="+entry1.getValue());
}
用keySet()迭代
Java代码
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
Java代码
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);               
}