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/*
* Copyright 2006-2012 Amazon Technologies, Inc. or its affiliates.
* Amazon, Amazon.com and Carbonado are trademarks or registered trademarks
* of Amazon Technologies, Inc. or its affiliates. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.amazon.carbonado.cursor;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.NoSuchElementException;
import com.amazon.carbonado.Cursor;
/**
* Special cursor implementation that is empty.
*
* @author Brian S O'Neill
* @see SingletonCursor
*/
public class EmptyCursor<S> implements Cursor<S> {
private static final Cursor EMPTY_CURSOR = new EmptyCursor();
/**
* Returns the empty cursor instance.
*/
@SuppressWarnings("unchecked")
public static <S> Cursor<S> the() {
return EMPTY_CURSOR;
}
// Package-private, to be used by test suite
EmptyCursor() {
}
/**
* Does nothing.
*/
public void close() {
}
/**
* Always returns false.
*/
public boolean hasNext() {
return false;
}
/**
* Always throws NoSuchElementException.
*/
public S next() {
throw new NoSuchElementException();
}
/**
* Always returns 0.
*/
public int skipNext(int amount) {
return 0;
}
/**
* Performs no copy and always returns 0.
*/
public int copyInto(Collection<? super S> c) {
return 0;
}
/**
* Performs no copy and always returns 0.
*/
public int copyInto(Collection<? super S> c, int limit) {
return 0;
}
/**
* Always returns an empty list.
*/
public List<S> toList() {
return Collections.emptyList();
}
/**
* Always returns an empty list.
*/
public List<S> toList(int limit) {
return Collections.emptyList();
}
}
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