mirror of git://gcc.gnu.org/git/gcc.git
91 lines
3.1 KiB
Java
91 lines
3.1 KiB
Java
/* EmptyEnumeration.java -- a constant empty enumeration
|
|
Copyright (C) 2001, 2002 Free Software Foundation, Inc.
|
|
|
|
This file is part of GNU Classpath.
|
|
|
|
GNU Classpath is free software; you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation; either version 2, or (at your option)
|
|
any later version.
|
|
|
|
GNU Classpath is distributed in the hope that it will be useful, but
|
|
WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with GNU Classpath; see the file COPYING. If not, write to the
|
|
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
|
|
02110-1301 USA.
|
|
|
|
Linking this library statically or dynamically with other modules is
|
|
making a combined work based on this library. Thus, the terms and
|
|
conditions of the GNU General Public License cover the whole
|
|
combination.
|
|
|
|
As a special exception, the copyright holders of this library give you
|
|
permission to link this library with independent modules to produce an
|
|
executable, regardless of the license terms of these independent
|
|
modules, and to copy and distribute the resulting executable under
|
|
terms of your choice, provided that you also meet, for each linked
|
|
independent module, the terms and conditions of the license of that
|
|
module. An independent module is a module which is not derived from
|
|
or based on this library. If you modify this library, you may extend
|
|
this exception to your version of the library, but you are not
|
|
obligated to do so. If you do not wish to do so, delete this
|
|
exception statement from your version. */
|
|
|
|
package gnu.java.util;
|
|
|
|
import java.io.Serializable;
|
|
import java.util.Enumeration;
|
|
import java.util.NoSuchElementException;
|
|
|
|
/**
|
|
* This is a helper class that produces an empty Enumerations. There is only
|
|
* one instance of this class that can be used whenever one needs a
|
|
* non-null but empty enumeration. Using this class prevents multiple
|
|
* small objects and inner classes. <code>getInstance()</code> returns
|
|
* the only instance of this class. It can be shared by multiple objects and
|
|
* threads.
|
|
*
|
|
* @author Mark Wielaard (mark@klomp.org)
|
|
*/
|
|
public final class EmptyEnumeration<T> implements Enumeration<T>, Serializable
|
|
{
|
|
/** The only instance of this class */
|
|
private static final EmptyEnumeration<Object> instance =
|
|
new EmptyEnumeration<Object>();
|
|
|
|
/**
|
|
* Returns an instance of this class for Object.
|
|
* It can be shared by multiple objects and threads.
|
|
*
|
|
* @return the common empty enumeration
|
|
*/
|
|
public static EmptyEnumeration<Object> getInstance()
|
|
{
|
|
return instance;
|
|
}
|
|
|
|
/**
|
|
* Returns false, since there are no elements.
|
|
*
|
|
* @return false
|
|
*/
|
|
public boolean hasMoreElements()
|
|
{
|
|
return false;
|
|
}
|
|
|
|
/**
|
|
* Always throws <code>NoSuchElementException</code>, since it is empty.
|
|
*
|
|
* @throws NoSuchElementException this is empty
|
|
*/
|
|
public T nextElement()
|
|
{
|
|
throw new NoSuchElementException();
|
|
}
|
|
}
|