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The Java Data Objects (JDO) API is a standard interface-based Java model abstraction of persistence, developed as Java Specification Request 243 under the auspices of the Java Community Process.

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */

/*
 * Extent.java
 *
 */

package javax.jdo;

import java.lang.Iterable;
import java.util.Iterator;

/** Instances of the Extent class represent the entire collection
 * of instances in the data store of the candidate class or interface
 * possibly including its subclasses or subinterfaces.
 * The Extent instance has two possible uses:
 * 

 * to iterate all instances of a particular class or interface
 * 
to execute a Query in the data store over all instances
 * of a particular class or interface
 * 
 * @version 2.1
 */
public interface Extent extends Iterable {
        
    /** Returns an iterator over all the instances in the Extent.
     * The behavior of the returned iterator might depend on the setting of the
     * ignoreCache flag in the owning PersistenceManager.
     * @return an iterator over all instances in the Extent
     */
    Iterator iterator();

    /** Returns whether this Extent was defined to contain subclasses.
     * @return true if this Extent was defined to contain instances
     * that are of a subclass type.
     */    
    boolean hasSubclasses();

    /** An Extent contains all instances of a particular class 
     * or interface in the data
     * store; this method returns the Class of the instances
     * represented by this Extent.
      * @return the Class of instances of this Extent.
      */
    Class getCandidateClass();

    /** An Extent is managed by a PersistenceManager;
     * this method gives access to the owning PersistenceManager.
     * @return the owning PersistenceManager
     */
    PersistenceManager getPersistenceManager();
    
    /** Close all Iterators associated with this Extent instance.
     * Iterators closed by this method will return false
     * to hasNext() and will throw
     * NoSuchElementException on next().
     * The Extent instance can still be used
     * as a parameter of Query.setExtent, and to get an Iterator.
     */    
    void closeAll ();
    
    /** Close an Iterator associated with this Extent instance.
     * Iterators closed by this method will return false
     * to hasNext() and will throw NoSuchElementException
     * on next(). The Extent instance can still be used
     * as a parameter of Query.setExtent, and to get an Iterator.
     * @param it an Iterator obtained by the method
     * iterator() on this Extent instance.
     */    
    void close (Iterator it);
    
    /** Get the fetch plan associated with this Extent.
     * @return the fetch plan
     * @since 2.0
     */
    FetchPlan getFetchPlan();
}