prefixmap.java

一个即时消息系统的源码（J2ME编程部分）。

package org.kxml;

import java.util.*;

/** Like Attribute, this class is immutable for similar reasons */

public class PrefixMap {

    Hashtable prefixMap;
    Hashtable namespaceMap;

    public PrefixMap () {
	prefixMap = new Hashtable ();
	namespaceMap = new Hashtable ();
    }


    public PrefixMap (PrefixMap base, String prefix, String namespace) {       

	prefixMap = clone (base.prefixMap);
	namespaceMap = clone (base.prefixMap);
	
	if (namespace == null) namespace = "";
	String oldNS = (String) prefixMap.get (prefix);
	if (oldNS == null) oldNS = "";
	
	if (!namespace.equals (oldNS)) {
	    
	    if (prefix.equals (namespaceMap.get (oldNS))) 
		namespaceMap.remove (oldNS);
	    
	    prefixMap.put (prefix, namespace);
	    namespaceMap.put (namespace, prefix);
	}
    } 


    private static Hashtable clone (Hashtable original) {

	Hashtable copy = new Hashtable (original.size () + 1);
	for (Enumeration e = original.keys (); e.hasMoreElements ();) {
	    Object key = e.nextElement ();
	    copy.put (key, original.get (key));
	}
	return copy;
    }


    public String getNamespace (String prefix) {
	String namespace = (String) prefixMap.get (prefix);
	return namespace == null ? Xml.NO_NAMESPACE : namespace;
    }


    public String getPrefix (String namespace) {
	return (String) namespaceMap.get 
	    (namespace == null ? "" : namespace);
    }


    public Enumeration prefixEnumeration () {
	return prefixMap.keys ();
    }
}