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Diffstat (limited to 'libjava/gnu/java')
-rw-r--r-- | libjava/gnu/java/util/EmptyEnumeration.java | 96 |
1 files changed, 96 insertions, 0 deletions
diff --git a/libjava/gnu/java/util/EmptyEnumeration.java b/libjava/gnu/java/util/EmptyEnumeration.java new file mode 100644 index 0000000..4e80499 --- /dev/null +++ b/libjava/gnu/java/util/EmptyEnumeration.java @@ -0,0 +1,96 @@ +/* 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., 59 Temple Place, Suite 330, Boston, MA +02111-1307 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 implements Enumeration, Serializable +{ + /** The only instance of this class */ + private static final EmptyEnumeration instance = new EmptyEnumeration(); + + /** + * Private constructor that creates a new empty Enumeration. + */ + private EmptyEnumeration() + { + } + + /** + * Returns the only instance of this class. + * It can be shared by multiple objects and threads. + * + * @return the common empty enumeration + */ + public static EmptyEnumeration 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 Object nextElement() + { + throw new NoSuchElementException(); + } +} |