wrappediterator.java

jena2.5.4推理机系统的一种最基本实现 HP实验室出品

/*
  (c) Copyright 2003, 2004, 2005, 2006, 2007 Hewlett-Packard Development Company, LP
  [See end of file]
  $Id: WrappedIterator.java,v 1.12 2007/01/02 11:49:41 andy_seaborne Exp $
*/

package com.hp.hpl.jena.util.iterator;

import java.util.*;

/**
    a WrappedIterator is an ExtendedIterator wrapping around a plain (or
    presented as plain) Iterator. The wrapping allows the usual extended
    operations (filtering, concatenating) to be done on an Iterator derived
    from some other source.
<br>
    @author kers
*/

public class WrappedIterator extends NiceIterator
    {
    /**
         set to <code>true</code> if this wrapping doesn't permit the use of 
         .remove(). Otherwise the .remove() is delegated to the base iterator.
    */
    protected boolean removeDenied;
    
    /**
        Answer an ExtendedIterator returning the elements of <code>it</code>.
        If <code>it</code> is itself an ExtendedIterator, return that; otherwise
        wrap <code>it</code>.
    */
    public static ExtendedIterator create( Iterator it )
        { return it instanceof ExtendedIterator ? (ExtendedIterator) it : new WrappedIterator( it, false ); }
    
    /**
        Answer an ExtendedIterator wrapped round <code>it</code> which does not
        permit <code>.remove()</code> even if <code>it</code> does.
    */
    public static WrappedIterator createNoRemove( Iterator it )
        { return new WrappedIterator( it, true ); }
      
    /** the base iterator that we wrap */  
    protected final Iterator base;
    
    public Iterator forTestingOnly_getBase()
        { return base; }
    
    /** constructor: remember the base iterator */
    protected WrappedIterator( Iterator base )
        { this( base, false ); }
    
    /**
         Initialise this wrapping with the given base iterator and remove-control.
         @param base the base iterator that this tierator wraps
         @param removeDenied true if .remove() must throw an exception
    */
    protected WrappedIterator( Iterator base, boolean removeDenied )
        { this.base = base; 
        this.removeDenied = removeDenied; }
        
    /** hasNext: defer to the base iterator */
    public boolean hasNext()
        { return base.hasNext(); }
        
    /** next: defer to the base iterator */
    public Object next()
        { return base.next(); }
        
    /** 
         if .remove() is allowed, delegate to the base iterator's .remove; 
         otherwise, throw an UnsupportedOperationException. 
    */
    public void remove()
        {
        if (removeDenied) throw new UnsupportedOperationException();
        base.remove(); 
        }
        
    /** close: defer to the base, iff it is closable */
    public void close()
        { close( base ); }

    /**
        if <code>it</code> is a Closableiterator, close it. Abstracts away from
        tests [that were] scattered through the code.
    */
    public static void close( Iterator it )
        { NiceIterator.close( it ); }
    }

/*
    (c) Copyright 2003, 2004, 2005, 2006, 2007 Hewlett-Packard Development Company, LP
    All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
    are met:

    1. Redistributions of source code must retain the above copyright
       notice, this list of conditions and the following disclaimer.

    2. Redistributions in binary form must reproduce the above copyright
       notice, this list of conditions and the following disclaimer in the
       documentation and/or other materials provided with the distribution.

    3. The name of the author may not be used to endorse or promote products
       derived from this software without specific prior written permission.

    THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
    IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
    IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
    NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
    THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/