propertiesiterator.java

swing编写的库存管理程序。毕业设计类

/**
 * ========================================
 * JFreeReport : a free Java report library
 * ========================================
 *
 * Project Info:  http://www.jfree.org/jfreereport/index.html
 * Project Lead:  Thomas Morgner;
 *
 * (C) Copyright 2000-2002, by Simba Management Limited and Contributors.
 *
 * This library is free software; you can redistribute it and/or modify it under the terms
 * of the GNU Lesser General Public License as published by the Free Software Foundation;
 * either version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License along with this
 * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * -----------------------
 * PropertiesIterator.java
 * -----------------------
 *
 * $Id: PropertiesIterator.java,v 1.2 2003/08/24 15:13:23 taqua Exp $
 *
 * Changes
 * -------
 * 20-Aug-2002 : Initial version
 * 22-Aug-2002 : Removed logging statements
 * 01-Sep-2002 : Documentation
 * 05-Sep-2002 : More documentation
 */
package org.jfree.report.util;

import java.util.Iterator;
import java.util.Properties;

/**
 * The properties iterator iterates over a set of enumerated properties. The properties are named
 * by an optional prefix plus a number, which is counted up on each iteration:
 * <ul>
 * <li>prefix_0
 * <li>prefix_1
 * <li>prefix_2
 * <li>...
 * </ul>
 * The iterator iterates over all subsequent numbered proprties until the number-sequence is
 * finished.
 *
 * @author Thomas Morgner
 */
public class PropertiesIterator implements Iterator
{
  /** The underlying properties collection. */
  private Properties properties;

  /** The property name prefix. */
  private String prefix;

  /** An incremental counter. */
  private int count;

  /**
   * Creates a new properties iterator without an prefix.
   *
   * @param properties  the underlying properties collection.
   */
  public PropertiesIterator(final Properties properties)
  {
    this(properties, null);
  }

  /**
   * Creates a new properties iterator with the given prefix.
   *
   * @param properties  the underlying properties collection.
   * @param prefix  a prefix for generating property names (null permitted).
   */
  public PropertiesIterator(final Properties properties, final String prefix)
  {
    if (properties == null)
    {
      throw new NullPointerException();
    }
    this.properties = properties;
    this.prefix = prefix;
    this.count = 0;
  }

  /**
   * Returns true if there is a property in the underlying collection with a name that matches
   * the name returned by the getNextKey() method.
   *
   * @return true if there is another property with a name in the correct form.
   */
  public boolean hasNext()
  {
    return properties.containsKey(getNextKey());
  }

  /**
   * Generates a property name in the form <prefix><count>.
   * <P>
   * The <count> begins at 0, and is automatically incremented with each call to the next() method.
   *
   * @return the next key in the sequence
   */
  private String getNextKey()
  {
    if (prefix == null)
    {
      return String.valueOf(count);
    }
    return prefix + String.valueOf(count);
  }

  /**
   * Returns the property with a name the same as the name generated by the getNextKey() method,
   * or null if there is no such property (that is, then end of the sequence has been reached).
   *
   * @return the property or null.
   */
  public Object next()
  {
    final String value = properties.getProperty(getNextKey());
    count++;
    return value;
  }

  /**
   * Always throws UnsupportedOperationException as remove is not implemented for this iterator.
   *
   * @throws UnsupportedOperationException as remove is not supported.
   */
  public void remove()
  {
    throw new UnsupportedOperationException();
  }

}