java遍历Map的几种方式

1.遍历map的几种方式:
private Hashtable<String, String> emails = new Hashtable<String, String>();

//方法一: 用entrySet()
Iterator it = emails.entrySet().iterator();
while(it.hasNext()){
Map.Entry m=(Map.Entry)it.next();
logger.info("email-" + m.getKey() + ":" + m.getValue());
}

// 方法二：直接再循环中
for (Map.Entry<String, String> m : emails.entrySet()) {
logger.info("email-" + m.getKey() + ":" + m.getValue());
}

// 方法三：用keySet()
Iterator it = emails.keySet().iterator();
while (it.hasNext()){
String key;
key=(String)it.next();
logger.info("email-" + key + ":" + emails.get(key));
}

//方法四：先把hashMap 转为集合Collection，再迭代输出，不过得到的是对象
Map aa = new HashMap();
aa.put("tmp1", new Object()); //追加 替换用同样的函数.
aa.remove("temp1"); //删除
for(Iterator i = aa.values().iterator(); i.hasNext();) {
Object temp = i.next();
} //遍历