Bug 149922 Image builder - URI and file source type are treated as same
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/util/StringUtil.java
* For example,
	 * <ul>
	 * <li>Both null and "" are empty strings
	 * <li>" " is not empty string.
	 * </ul>
	 * 
	 * @param value
	 *            the string to check
	 * @return true if the string is empty, false otherwise.
	 */
	public static boolean isEmpty( String value )
	{
		if ( value == null || value.length( ) == 0 )
			return true;
		return false;
	}
	/**
	 * Returns if the two string are null or equal. The
	 * {@link java.lang.String#equals(String)}is used to compare two strings.
	 * 
	 * @param str1
	 *            the string to compare
	 * @param str2
	 *            the string to compare
	 * @return true, if the two string are null, or the two string are equal
	 *         with case sensitive.
	 */
	public static boolean isEqual( String str1, String str2 )
	{
		return str1 == str2 || ( str1 != null && str1.equals( str2 ) );