Enumeration

AI-generated Key Takeaways

• Enumeration is an interface in Java that allows you to access elements of a collection one by one, such as elements in a Vector or keys/values in a Hashtable.

• It provides two main methods: hasMoreElements() to check if there are more elements and nextElement() to retrieve the next element.

• While functional, Enumeration is considered a legacy interface and new implementations are encouraged to utilize the Iterator interface instead, which offers similar functionality with enhancements like a remove operation and shorter method names.

• Despite being older, Enumeration is still used in certain legacy systems and provides a basic framework for iterating over collections of objects.

public interface Enumeration

Known Indirect Subclasses StringTokenizer StringTokenizer The string tokenizer class allows an application to break a string into tokens.

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.

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.

See Also

• Iterator
• SequenceInputStream
• nextElement()
• Hashtable
• Hashtable.elements()
• Hashtable.keys()
• Vector
• Vector.elements()

Public Method Summary

abstract boolean	hasMoreElements() Tests if this enumeration contains more elements.
abstract E	nextElement() Returns the next element of this enumeration if this enumeration object has at least one more element to provide.

Public Methods

public abstract 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.

public abstract E 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.