Iterates a filename

FileNameIterator

/**
	 * Rather unneccessary, but delightfully interesting (and efficient) way to
	 * iterate the number at the end of a file name.  At least I expect it to be
	 * efficient since it utilizes a single character buffer all the way through.
	 *
	 * It does this by using, underneath everything, javas fast array copy methods
	 * via StringBuilder, and then through slicing and reversing the string to 
	 * abstract out the number at the end of a fileName.  So a File Name of the 
	 * format FileName1234.txt will automatically be parsed and return 
	 * FileName1235.txt.
	 *
	 * Not all possible edge cases have been investigated however.
	 *
	 * @param fileName
	 * @return a new FilenName, one greater.
	 */
	static String fileNameIterator( String fileName ){
		Pattern COMPILE =
						Pattern.compile( "(\\.)" );
		String   defaultFileName = "LogFile765.txt";
		String[] fn              = COMPILE.split( fileName );
		//48-57
		//fn[0].charAt( (fn[0].length()-1) )
		System.out.println( fn.length );
		String        temp          = fn[ 0 ];
		StringBuilder stringBuilder = new StringBuilder( temp );
		temp = stringBuilder
						       .reverse()
						       .toString();
		stringBuilder.setLength( 0 );
		while( Character.isDigit( temp.charAt( 0 ) ) ){
			stringBuilder.append( temp.charAt( 0 ) );
			temp = temp.substring( 1 ); //cut off one digit from the front
		}
		if( stringBuilder.length() >= 1 ){
			stringBuilder
							.reverse()
							.replace( 0 , stringBuilder.length() ,
							          String.valueOf( Integer.parseInt( stringBuilder.toString() ) + 1 )
							        )
							.reverse() //reverse it backwards again since filename is still
							// rev.
							.append( temp )  //append the nonnumerial part
							.reverse()
							.append( "." ) //add the extension
							.append( fn[ 1 ] ); //reappend the filename
		} else{
			stringBuilder
							.append( fn[ 0 ] )
							.append( 001 )
							.append( "." )
							.append( fn[ 1 ] );
		}
		return stringBuilder.toString();
	}