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docx4j is a library which helps you to work with the Office Open XML file format as used in docx documents, pptx presentations, and xlsx spreadsheets.

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/*
 * This file is part of the DiffX library.
 *
 * For licensing information please see the file license.txt included in the release.
 * A copy of this licence can also be found at
 *   http://www.opensource.org/licenses/artistic-license-2.0.php
 */
package com.topologi.diffx.sequence;

import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;

/**
 * Provides a mapping of namespace URIs to prefixes.
 * 
 * This class can be used to reconstruct the qualified element or attribute names.
 * 
 * 
Note that for each namespace URI there can only be one prefix.
 * 
 * @author Christophe Lauret
 * @version 12 May 2010
 * 
 * @since 0.7
 */
public final class PrefixMapping {

  /**
   * Maps namespace URIs to prefixes.
   */
  private final Map mappings = new HashMap();

  /**
   * Add the specified mapping if the namespace URI has not been mapped before.
   * 
   * This method will ensure that the mapping is actually unique, that is that
   * the namespace URI correspond to one and only one prefix and that the prefix only
   * corresponds to one and only one namespace URI.
   * 
   * @param uri    The namespace URI to map.
   * @param prefix The prefix to use.
   * 
   * @throws NullPointerException if the URI or prefix is null
   */
  public void add(String uri, String prefix) throws NullPointerException {
    if (!this.mappings.containsKey(uri)) {
      int count = 0;
      String actualPrefix = prefix;
      while (this.mappings.containsValue(actualPrefix)) {
        actualPrefix = prefix + count++;
      }
      this.mappings.put(uri, actualPrefix);
    }
  }

  /**
   * Returns an enumeration of the namespace URIs used in this mapping.
   * 
   * @return An enumeration of the namespace URIs used in this mapping.
   */
  public Enumeration getURIs() {
    return Collections.enumeration(this.mappings.keySet());
  }

  /**
   * Returns the prefix corresponding to the given namespace URI.
   * 
   * @param uri The namespace URI to map.
   * 
   * @return The corresponding prefix.
   */
  public String getPrefix(String uri) {
    return uri == null? "" : this.mappings.get(uri);
  }

}