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Class collections.MappingEnumeration

java.lang.Object
   |
   +----collections.MappingEnumeration

public class MappingEnumeration

extends Object

implements Enumeration

MappingEnumerations work as wrappers around other Enumerations. To build one, you need an existing Enumeration (perhaps one from coll.elements(), for some Collection coll), and a Function object (i.e., implementing interface Function). For example, if you want to process only the parent() fields of java.awt.Component elements held by a collection coll you could write something of the form:

 Enumeration e = coll.elements();
 Enumeration parents = MappingEnumeration(e, ParentFunction);
 while (parents.hasMoreElements()) 
  doSomethingWith((Container)(parents.nextElement()));
 

 class ParentFunction implements Function {
  Object function(Object v) {
    if (v instanceOf Component) return ((Component)v).getParent();
    else return null;
  }
 }
 

(This requires too much set-up to be reasonable in most situations, but is invaluable in others.)

See Also:

function

MappingEnumeration(Enumeration, Function)

Make an enumeration wrapping src, returning p.function for each nextElement

hasMoreElements()

Implements java.util.Enumeration.hasMoreElements

nextElement()

Implements java.util.Enumeration.nextElement.

 public MappingEnumeration(Enumeration src,
                           Function p)

Make an enumeration wrapping src, returning p.function for each nextElement

 public synchronized boolean hasMoreElements()

Implements java.util.Enumeration.hasMoreElements

 public synchronized Object nextElement()

Implements java.util.Enumeration.nextElement.

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