[java] iterating through Enumeration of hastable keys throws NoSuchElementException error

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","[email protected]");
vars.put("DOB","02 Mar 1983");

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

while(e.hasMoreElements()){

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

Console output:

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)

You're calling nextElement twice in the loop. You should call it only once, else it moves ahead twice:

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

You are calling nextElement twice. Refactor like this:

while(e.hasMoreElements()){


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

for (String key : Collections.list(e))
    System.out.println(key);

Each time you do e.nextElement() you skip one. So you skip two elements in each iteration of your loop.

Every time you call e.nextElement() you take the next object from the iterator. You have to check e.hasMoreElement() between each call.

Example:

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

You're calling e.nextElement() twice inside your loop when you're only guaranteed that you can call it once without an exception. Rewrite the loop like so:

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