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/*******************************************************************************
* Copyright (c) 2007 Oracle. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0, which accompanies this distribution
* and is available at http://www.eclipse.org/legal/epl-v10.html.
*
* Contributors:
* Oracle - initial API and implementation
******************************************************************************/
package org.eclipse.jpt.utility.internal.model.value;
import org.eclipse.jpt.utility.internal.iterators.EmptyListIterator;
/**
* A read-only list value model for when you don't
* need to support a list.
*/
public final class NullListValueModel
extends AbstractReadOnlyListValueModel
{
private static final long serialVersionUID = 1L;
// singleton
private static NullListValueModel INSTANCE;
/**
* Return the singleton.
*/
public static synchronized ListValueModel instance() {
if (INSTANCE == null) {
INSTANCE = new NullListValueModel();
}
return INSTANCE;
}
/**
* Ensure non-instantiability.
*/
private NullListValueModel() {
super();
}
// ********** ListValueModel implementation **********
@Override
public int size() {
return 0;
}
public Object getValue() {
return EmptyListIterator.instance();
}
// ********** Object overrides **********
@Override
public String toString() {
return "NullListValueModel";
}
/**
* Serializable singleton support
*/
private Object readResolve() {
return instance();
}
}
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