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Interface Enumeration<E>
- Type Parameters:
E - the type of elements returned by this enumeration
- All Known Subinterfaces:
NamingEnumeration<T>
- All Known Implementing Classes:
StringTokenizer
public interface Enumeration<E>
An object that implements the Enumeration interface generates a
series of elements, one at a time. Successive calls to the
nextElement method return successive elements of the
series.
For example, to print all elements of a Vector<E> v:
for (Enumeration<E> e = v.elements(); e.hasMoreElements();)
System.out.println(e.nextElement());
Methods are provided to enumerate through the elements of a
vector, the keys of a hashtable, and the values in a hashtable.
Enumerations are also used to specify the input streams to a
SequenceInputStream.
- API Note:
- The functionality of this interface is duplicated by the
Iterator
interface. In addition, Iterator adds an optional remove operation,
and has shorter method names. New implementations should consider using
Iterator in preference to Enumeration. It is possible to
adapt an Enumeration to an Iterator by using the
asIterator() method.
- Since:
- 1.0
- See Also:
-
-
Method Summary
Modifier and Type
Method
Description
Returns an
Iterator that traverses the remaining elements
covered by this enumeration.
boolean
Tests if this enumeration contains more elements.
Returns the next element of this enumeration if this enumeration
object has at least one more element to provide.
-
Method Details
-
hasMoreElements
boolean hasMoreElements()
Tests if this enumeration contains more elements.
- Returns:
true if and only if this enumeration object
contains at least one more element to provide;
false otherwise.
-
nextElement
Returns the next element of this enumeration if this enumeration
object has at least one more element to provide.
- Returns:
- the next element of this enumeration.
- Throws:
NoSuchElementException - if no more elements exist.
-
asIterator
Returns an
Iterator that traverses the remaining elements
covered by this enumeration. Traversal is undefined if any methods
are called on this enumeration after the call to
asIterator.
- API Note:
- This method is intended to help adapt code that produces
Enumeration instances to code that consumes Iterator
instances. For example, the JarFile.entries() method returns an Enumeration<JarEntry>.
This can be turned into an Iterator, and then the
forEachRemaining() method can be used:
JarFile jarFile = ... ;
jarFile.entries().asIterator().forEachRemaining(entry -> { ... });
(Note that there is also a JarFile.stream() method that returns a Stream of entries,
which may be more convenient in some cases.)
- Implementation Requirements:
- The default implementation returns an
Iterator whose
hasNext method calls this Enumeration's
hasMoreElements method, whose next
method calls this Enumeration's nextElement method, and
whose remove method throws
UnsupportedOperationException.
- Returns:
- an Iterator representing the remaining elements of this Enumeration
- Since:
- 9