java recursive rle decompress

public static String decompress(String compressedText)
	{
		char c = compressedText.charAt(0);

		if(compressedText.length() == 1)
		{
			return compressedText;
		}

		else
		{
			if(Character.isLetter(c) == true)
			{
				return c + decompress(compressedText.substring(1));
			}

			else
			{
				compressedText = c-1 + compressedText.substring(1);

				return compressedText.substring(1, 2) + decompress(compressedText);
			}
		}

	}