Enumeration interface

 

 

Enumerations are used for Vector (which is a List) and Stack (also a List).

 

■ You must always explicitly cast all returned elements.

 

■ You cannot remove elements with Enumerations (unlike with the newer iterators)

 

 

.elements( ),  .hasMoreElements( )  and  .nextElement( )   methods

 

vh.elements( )  returns an enumerator.  i.e.  assume a Vector v

 

Enumeration e = v.elements( );

while (e.hasMoreElements( )) {

if ( (ObjectCastHere) (e.nextElement( ) ) == gotcha) then do something; } 

or ... Object element = (YourObjectCast) e.nextElement( );

 

e.nextElement( ) throws a NoSuchElementException after the end, so you need a try-catch here.

 

import java.util.*;

 

try {

Vector v = new Vector( );

v.add( "AA" );

v.add( "BB" );

v.add( "CC" );

v.add( "DD" );

Enumeration e = v.elements( );

 

while ( e.hasMoreElements( ) ) {

Object element = (Object) e.nextElement( );

System.out.println(element); }                           //prints => AA BB CC DD

 

}

catch (Exception e) {  }