stringutils.java

老外的在线考试

/*
 * Core - Library of useful classes that are used in many CyberDemia projects.
 * Copyright (C) 2004 CyberDemia Research and Services
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 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
 * Library General Public License for more details.
 * 
 * You should have received a copy of the GNU Library 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.
 *
 * See the COPYING file located in the top-level-directory of
 * the archive of this library for complete text of license.
 */
package com.cyberdemia.util;


/**
 * StringUtils is a utility class for manipulating Strings.
 * 
 * @author Alexander Yap
 * @version $Revision: 1.2 $ at $Date: 2004/06/12 12:51:56 $ by $Author: alexycyap $
 */
public abstract class StringUtils
{
	private StringUtils() 
    { 
	    // Not used
    }
	
	/**
	 * Truncates the src String to a maximum of length characters.
	 * If src's length is shorter than or equals to length, it is returned unchanged.
	 * If src is longer than length, is it truncated to (length-3) characters and 
	 * then the suffix "..." is appended to the end to form the resultant String.
	 * 
	 * @param src Original String
	 * @param length Length to truncate to, must be at least 3.
	 * @return Truncated String.
	 * @throws IllegalArgumentException if length is less than 3.
	 */
	public static String truncate(String src, int length)
	{
		if (length<3)
		{
			throw new IllegalArgumentException("Argument length is too short, must be 3 or more.");
		}
		
		if (src.length()<=length)
		{
			return src;
		}
		
		return src.substring(0,length-3) + "...";
	}
	
	/**
	 * Escapes HTML sensitive characters within an input String and returns 
	 * a String suitable to be used in a HTML page. 
	 * @param inStr  Input String 
	 * @param escapeSpace true to escape space characters as non-breaking-spaces (preventing word wrapping), false to keep them as spaces.
	 * @return String suitable to be used in a HTML page.
	 */
	public static String escapeHTML(String inStr, boolean escapeSpace)
	{
		char[] inChars = inStr.toCharArray();
		StringBuffer buf = new StringBuffer(inChars.length);
		for (int i=0; i<inChars.length; i++)
		{
			char c = inChars[i];
			if ( (c==' ') || Character.isLetterOrDigit(c) )
			{
				if ((c==' ') && escapeSpace)
				{
					buf.append("&nbsp;");
				}
				else
				{
					buf.append(c);
				}
			}
			else
			{
				switch (c)
				{
					case '<':
						buf.append("&lt;");
						break;
					case '>':
						buf.append("&gt;");
						break;
					case '\n':
						buf.append("<br />");
						break;
					case '"':
						buf.append("&quot;");
						break;
					case '&':
						buf.append("&amp;");
						break;
					default:
						// Unicode 
						buf.append("&#");
						buf.append(String.valueOf((int)c));
						buf.append(';');
				}
			}		
		}
		return buf.toString();
	}
	
}