package rtree;import java.util.*;/** * Implements a memory page file. Holds all pages into a Hashtable with keys equal to each object's * page number. * <p> * Created: Wed May 19 09:33:26 1999 * <p> * @author Hadjieleftheriou Marios * @version 1.002 */public class MemoryPageFile extends PageFile {    private Hashtable file = new Hashtable();    protected void initialize(RTree tree, int dimension, float fillFactor, int capacity, int treeType) {	super.initialize(tree, dimension, fillFactor, capacity, treeType);	file.clear();    }    /*    protected byte[] readData(int page) throws PageFaultError {	if (page < 0) {	    throw new IllegalArgumentException("Page number cannot be negative.");	}	byte[] ret = (byte[]) file.get(new Integer(page));	if (ret == null) {	    throw new PageFaultError("Invalid page number request.");	}	return ret;    }    protected int writeData(byte[] d, int page) throws PageFaultError {	if (d == null) {	    throw new IllegalArgumentException("Data cannot be null.");	}	if (page < 0) {	    page = 0;	    while (true) {		if (! file.containsKey(new Integer(page))) {		    break;		}		page++;	    }	}		file.put(new Integer(page), d);	return page;    }    */    protected AbstractNode readNode(int page) throws PageFaultError {	if (page < 0) {	    throw new IllegalArgumentException("Page number cannot be negative.");	}	AbstractNode ret = (AbstractNode) file.get(new Integer(page));	if (ret == null) {	    throw new PageFaultError("Invalid page number request.");	}	return ret;    }    protected int writeNode(AbstractNode n) throws PageFaultError {	if (n == null) {	    throw new IllegalArgumentException("Node cannot be null.");	}	int i = 0;	if (n.pageNumber < 0) {	    while (true) {		if (! file.containsKey(new Integer(i))) {		    break;		}		i++;	    }	    n.pageNumber = i;	} else {	    i = n.pageNumber;	}	file.put(new Integer(i), n);	return i;    }    protected AbstractNode deletePage(int page) throws PageFaultError {	return (AbstractNode) file.remove(new Integer(page));    }    public void dumpMemory() {	for (Enumeration e = file.elements(); e.hasMoreElements();) {	    System.out.println(e.nextElement());	}    }} // MemoryPageFile