Java四舍五入小工具

Java实现四舍五入，有什么不足恳请指正

public class RoundTool {
	public static String round(double num, int dotNum) {
		double temp = 1.0;//用于五入时直接进位
		for (int i = 0; i < dotNum; i++) {
			temp = temp / 10;
		}
		String strNum = String.valueOf(num);
		int dotLoca = strNum.indexOf(".");// 确定小数点位置
		String beforStr = null;
		if ((strNum.substring(dotLoca)).length() - 1 > dotNum) {// 如果给出的数小数点位数大于要求保留小数点位数
			beforStr = strNum.substring(0, dotLoca + dotNum + 1);// 从头开始截取所要求保留小数点前一位
			String endStr = strNum.substring(dotLoca + dotNum + 1, dotLoca
					+ dotNum + 2);// 截取要求保留小数位数后一位
			if (Integer.parseInt(endStr) >= 5) {//五入
				double beforTemp = Double.valueOf(beforStr);
				beforStr = String.valueOf(beforTemp +  temp);
			}
			if (beforStr.substring(dotLoca).length() -1< dotNum) {//五入后小数点后几位0自动舍去后补足
				int intTemp = dotNum - beforStr.substring(dotLoca).length() + 1;
				for (int i = 0; i < intTemp; i++) {
					beforStr = beforStr + 0;
				}
			}
		} else {//给出数小数点位数不足需保留位数补0
			beforStr = strNum;
			int intTemp = dotNum - beforStr.substring(dotLoca).length() + 1;
			for (int i = 0; i < intTemp; i++) {
				beforStr = beforStr + 0;
			}
		}
		return beforStr.substring(0,dotLoca+dotNum+1);
	}

	public static void main(String[] args) {
		System.out.println(RoundTool.round(123.456789, 3));
	}
}