java - 遍历 hastable 键的枚举会引发 NoSuchElementException 错误

Question

我正在尝试使用枚举从哈希表中迭代一个键列表，但是我在列表中的最后一个键处不断收到 NoSuchElementException？

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

vars.put("POSTCODE","TU1 3ZU");
vars.put("EMAIL","job.blogs@lumesse.com");
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:

EMAILPOSTCODE

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

Answer 1

您在循环中调用了两次 nextElement()。此调用将枚举指针向前移动。你应该像下面这样修改你的代码:

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