NumberUtils 计算相关

加、减、乘、除、四舍五入、格式化数字

/*
 * setScale(2, roundMode); 如2.355655
 * ROUND_CEILING
 * ROUND_DOWN       2.35
 * ROUND_FLOOR
 * ROUND_HALF_DOWN  2.35
 * ROUND_HALF_EVEN
 * ROUND_HALF_UP   四舍五入 2.36
 * ROUND_UNNECESSARY    2.355655
 * ROUND_UP    进位 2.36
 */

public class NumberUtils {

    /**
     * 加
     */
    public static String addNumber(Object number1, Object number2) {
        String result = new BigDecimal(number1 + "")
                .add(new BigDecimal(number2 + ""))
                .toPlainString();
        return removeZeroAfterDot(result);
    }

    /**
     * 减
     */
    public static String subtractNumber(Object number1, Object number2) {
        String result = new BigDecimal(number1 + "")
                .subtract(new BigDecimal(number2 + ""))
                .toPlainString();
        return removeZeroAfterDot(result);
    }

    /**
     * 乘
     */
    public static String multiplyNumber(Object number1, Object number2) {
        String result = new BigDecimal(number1 + "")
                .multiply(new BigDecimal(number2 + ""))
                .toPlainString();
        return removeZeroAfterDot(result);
    }

    /**
     * 除
     * @param scale BigDecimal.
     */
    public static String divideNumber(Object number1, Object number2, int scale) throws IllegalAccessException {
        if (scale < 0) {
            throw new IllegalAccessException("精确度不能小于0");
        }
        String result = new BigDecimal(number1 + "")
                .divide(new BigDecimal(number2 + ""), BigDecimal.ROUND_HALF_UP)
                .toPlainString();
        return removeZeroAfterDot(result);
    }

    /**
     * 去掉小数点后的0
     */
    public static String removeZeroAfterDot(Object s) {
        if (s.toString().indexOf(".") > 0) {
            s = s.toString().replaceAll("0+?$", "");   //去掉后面无用的零
            s = s.toString().replaceAll("[.]$", "");   //如小数点后面全是零则去掉小数点
        }
        return s.toString();
    }

    /**
     * 格式化显示小数点后的0的个数
     * @param number 数字
     * @param count  小数的个数
     */
    public static String formatNumber(Object number, int count) {
        if (TextUtils.isEmpty(number + "")) {
            return "0";
        }
        StringBuilder sb = new StringBuilder();
        if (count == 0) {
            sb.append("0");
        } else {
            sb.append("0.");
            for (int i = 0; i < count; i++) {
                sb.append(0);
            }
        }
        return roundNumber(number, sb.toString());
    }

    /**
     * 四舍五入取小数格式
     * @param number
     * @param pattern "#.##"(会去掉末位的0) / "0.00"
     */
    public static String roundNumber(Object number, String pattern) {
        DecimalFormat df = new DecimalFormat(pattern);
        if (number instanceof String) {
            if (!TextUtils.isEmpty((String) number)) {
                return df.format(Double.parseDouble((String) number));
            }
        }
        if (TextUtils.isEmpty(number + "")) {
            return "";
        }
        return df.format(number);
    }
}

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