Synopsis

Interface Name:

java.util.Enumeration

Super-interface:

None

Immediate Sub-interfaces:

None

Implemented By:

java.util.StringTokenizer

Availability:

JDK 1.0 or later

Description

An object that implements the Enumeration interface provides a way to access a set of objects sequentially. The Enumeration object hides the actual organization of the set of objects from the code that is using it. An Enumeration can iterate through, or enumerate, its set of objects one at a time. A specific implementation of the interface controls the order in which the objects are presented.

The following is an example of how an Enumeration is used. The example shows a method for printing the values in an Enumeration:

void printAll(Enumeration e) {
    while ( e.hasMoreElements() ) {
        System.out.println(e.nextElement());
    }
}

Note that an Enumeration can be used only once: it iterates through its collection of objects in one direction and cannot be reset or rewound.

Normally, an Enumeration is not instantiated directly, but instead returned by a method that needs to enumerate a set of values. For example, the elements() method of the Vector class returns an Enumeration of the elements in the Vector. By the same token, the elements() and keys() methods of the Hashtable class return Enumeration objects for the keys and values in the Hashtable.

Interface Declaration

public abstract interface java.util.Enumeration {
  // Methods
  public abstract boolean hasMoreElements();
  public abstract Object nextElement() throws NoSuchElementException;
}

Methods

See Also

Hashtable, StringTokenizer, Vector