android提取字符串中为字母的字符

	/**
	 * 提取字符串中为字母的字符
	 */
	private static String returnResultMultiple(String str) {
		String string = "";
		if (str.equals("")) {
			return "";
		}
		for (int i = 0; i < str.length(); i++) {
			char ch = str.charAt(i);
			if (Character.isLetter(ch)) {
				string = string + ch;
			}
		}
		return string;
	}