迭代通过枚举hastable键会抛出NoSuchElementException错误 [英] iterating through Enumeration of hastable keys throws NoSuchElementException error

问题描述

我正在尝试使用枚举来遍历散列表中的键列表但是我一直在列表的最后一个键处获得NoSuchElementException？

I am trying to iterate through a list of keys from a hash table using enumeration however I keep getting a NoSuchElementException at the last key in list?

Hashtable<String, String> vars = new Hashtable<String, String>();

vars.put("POSTCODE","TU1 3ZU");
vars.put("EMAIL","[e-mail]");
vars.put("DOB","02 Mar 1983");

Enumeration<String> e = vars.keys();

while(e.hasMoreElements()){

System.out.println(e.nextElement());
String param = (String) e.nextElement();
}

控制台输出：

EMAIL
POSTCODE

Exception in thread "main" java.util.NoSuchElementException: Hashtable Enumerator
    at java.util.Hashtable$Enumerator.nextElement(Unknown Source)
    at testscripts.webdrivertest.main(webdrivertest.java:47)

推荐答案

你打电话给 nextElement（）两次环。此调用将枚举指针向前移动。
您应修改以下代码：

You call nextElement() twice in your loop. This call moves the enumeration pointer forward. You should modify your code like the following:

while (e.hasMoreElements()) {
    String param = e.nextElement();
    System.out.println(param);
}

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