/* Copyright 2013 The jeo project. 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 io.jeo.data;
import java.io.IOException;
import java.util.Collection;
import java.util.Iterator;
/**
* Utility class for {@link Cursor} objects.
*
* @author Justin Deoliveira, OpenGeo
*/
public class Cursors {
/**
* Returns a empty cursor object.
*/
public static <T> Cursor<T> empty() {
return new Cursor<T>() {
@Override
public boolean hasNext() throws IOException {
return false;
}
@Override
public T next() throws IOException {
return null;
}
@Override
public void close() {
}
};
}
/**
* Returns a cursor containing a single object.
*/
public static <T> Cursor<T> single(T obj) {
return new SingleCursor<T>(obj);
}
private static class SingleCursor<T> extends Cursor<T> {
T obj;
SingleCursor(T obj) {
this.obj = obj;
}
@Override
public boolean hasNext() throws IOException {
return obj != null;
}
@Override
public T next() throws IOException {
try {
return obj;
}
finally {
obj = null;
}
}
@Override
public void close() {
}
}
/**
* Creates a cursor from an existing collection.
*/
public static <T> Cursor<T> create(Collection<T> collection) {
return create(collection.iterator());
}
/**
* Creates a cursor from an existing iterator.
*/
public static <T> Cursor<T> create(Iterator<T> it) {
return new IteratorCursor<T>(it);
}
private static class IteratorCursor<T> extends Cursor<T> {
Iterator<T> it;
IteratorCursor(Iterator<T> it) {
this.it = it;
}
@Override
public Iterator<T> iterator() {
return it;
}
@Override
public boolean hasNext() throws IOException {
return it.hasNext();
}
@Override
public T next() throws IOException {
return it.next();
}
@Override
public void close() {
}
}
}