java截取字符串前面的数字

/**
	 * 截取字符串前面的正整数，如"22天"得"22","18个人"得到"18".
	 * @return
	 */
	public static String getQuantity(String regular){
		int index = 0;
		for (int i = 0; i < regular.length(); i++) {
			char c = regular.charAt(i);
			if (Character.isDigit(c)) {
				if (i == regular.length() - 1) {
					index = i + 1;
				} else {
					index = i;
				}
				continue;
			} else {
				index = i;
				break;
			}
		}
		return regular.substring(0, index);
	}