OpenJDK 27 · java.util.Enumeration · APIdia, the JavaDoc alternative

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.

Method Summary

Modifier and Type	Method and Description
public default Iterator<E>	Returns: an Iterator representing the remaining elements of this Enumeration asIterator() Returns an `Iterator` that traverses the remaining elements covered by this enumeration.
public boolean	Returns: `true` if and only if this enumeration object contains at least one more element to provide; `false` otherwise. hasMoreElements() Tests if this enumeration contains more elements.
public E	Returns: the next element of this enumeration. nextElement() Returns the next element of this enumeration if this enumeration object has at least one more element to provide.

Method Detail

asIterator back to summary

asIterator	back to summary
public default Iterator<E> 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 Specification 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:Iterator<E> an Iterator representing the remaining elements of this Enumeration Since 9

public default Iterator<E> 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 Specification

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:Iterator<E>: an Iterator representing the remaining elements of this Enumeration
Since: 9

hasMoreElements back to summary

hasMoreElements	back to summary
public boolean hasMoreElements() Tests if this enumeration contains more elements. Returns:boolean `true` if and only if this enumeration object contains at least one more element to provide; `false` otherwise.

public boolean hasMoreElements()

Tests if this enumeration contains more elements.

Returns:boolean: true if and only if this enumeration object contains at least one more element to provide; false otherwise.

nextElement	back to summary
public E nextElement() Returns the next element of this enumeration if this enumeration object has at least one more element to provide. Returns:E the next element of this enumeration. Exceptions NoSuchElementException: if no more elements exist.

nextElement

back to summary

public E nextElement()

Returns the next element of this enumeration if this enumeration object has at least one more element to provide.

Returns:E

the next element of this enumeration.

Exceptions

NoSuchElementException:: if no more elements exist.

public Interface Enumeration<E>

Method Summary

Method Detail