21.1 The Interface java.util.Enumeration
An object that implements the Enumeration
interface will generate a series of elements, one at a time. Successive calls to the nextElement
method will return successive elements of the series.
public interface Enumeration {
public boolean hasMoreElements();
public Object nextElement() throws NoSuchElementException;
}
21.1.1 public boolean hasMoreElements()
The result is true
if and only if this enumeration object has at least one more element to provide.
21.1.2 public Object nextElement()throws NoSuchElementException
If this enumeration object has at least one more element to provide, such an element is returned; otherwise, a NoSuchElementException
is thrown.
As an example, the following code prints every key in the hashtable ht
and its length. The method keys
returns an enumeration that will deliver all the keys, and we suppose that the keys are, in this case, known to be strings:
Enumeration e = ht.keys();
while (e.hasMoreElements()) {
String key = (String)e.nextElement();
System.out.println(key + " " + key.length());
}