A DESCRIPTION OF THE REQUEST :
I think that it would be nice if the java util classes had this:

new interface

public interface java.util.Filter<Object T> {
    public boolean accept(T item);
}

new methods on java.util.Collection<Object T>
    public void addAll(Iterable<T> src, Filter<T> filter);
    public void addAll(Iterator<T> iterator); // if it isn't already there
    public Iterator iterator(Filter<T> filter);

new method on java.util.Collections
    public static <T> Iterator<T> filter(Iterator<T> iterator, Filter<T> filter) // not 100% sure about the generics syntax

new methods on java.io.File
    String[] list(Filter<String> filter);
    File[] listFiles(Filter<File> filter);

Deprecate classes FileFilter and FileNameFilter, but have the deprecated classes implement Filter<File> and Filter<String> for now. Deprecate list(FileNameFilter ) and listFiles(FileFilter).

JUSTIFICATION :
This would provide a standard interface for a common programming task. I'm sure there are other places in the APIs where this would be appropriate.

I note that bug 5053833 has been marked not fixed because the standard libraties should not be doing set theory.

Might I however suggest a new Method on java.util.Collections:

    public static Iterator concatenate(Iterable a, Iterable b)

 


CUSTOMER SUBMITTED WORKAROUND :
Roll your own class
Posted Date : 2005-11-15 11:30:13.0

N/A

A reasonable request.

Note that Java has no special support for first-class functions,
and so such features as the one proposed here are less compelling.
Posted Date : 2006-02-03 05:04:46.0

Support for first class functions would be compelling...