数字处理方法类

package numTest;

import java.math.BigDecimal;

/**
 * 高精度计算辅助类，提供保留指定小数位的简单计算和四舍五入
 */
public class Num {
    private static final BigDecimal one = new BigDecimal(1);
    private BigDecimal decimal;
    private int scale;
    private int roundingMode = BigDecimal.ROUND_HALF_UP;

    public Num() {
        decimal = new BigDecimal(0);
    }

    public Num(double val) {
        this.decimal = new BigDecimal(val);
    }

   /* public Num(double val, int scale) {
        this.scale = scale;
        this.decimal = new BigDecimal(val).setScale(scale, roundingMode);
    }*/

    public Num(double val, int scale, int roundingMode) {
        this.scale = scale;
        this.roundingMode = roundingMode;
        this.decimal = new BigDecimal(val).setScale(scale, roundingMode);
    }

    public Num(Num num, int scale, int roundingMode) {
        decimal = num.decimal.setScale(scale, roundingMode);
    }

    public BigDecimal getDecimal() {
        return decimal;
    }

    public Num setDecimal(BigDecimal decimal) {
        this.decimal = decimal;
        return this;
    }

    public int getScale() {
        return scale;
    }

    public void setScale(int scale) {
        this.scale = scale;
        this.decimal = this.decimal.setScale(scale);
    }

    public double doubleValue() {
        return decimal.doubleValue();
    }

    public Num divide(Num num) {
        return divide(setOtherNum(num), scale, roundingMode);
    }

    public Num divide(double val) {
        Num num = new Num(val);
        return divide(num);
    }

    public Num divide(Num num, int scale) {
        return divide(num, scale, roundingMode);
    }

    public Num divide(Num num, int scale, int roundingMode) {
        return setDecimal(this.getDecimal().divide(num.getDecimal(), scale, roundingMode));
    }

    public Num multiply(Num num) {
        return multiply(setOtherNum(num), scale, roundingMode);
    }

    public Num multiply(double val) {
        Num num = new Num(val);
        return multiply(num);
    }

    public Num multiply(Num num, int scale) {
        return multiply(num, scale, roundingMode);
    }

    public Num multiply(Num num, int scale, int roundingMode) {
        return setDecimal(rounding(this.getDecimal().multiply(num.getDecimal()), scale, roundingMode));
    }

    public Num add(Num num) {
        return add(setOtherNum(num), scale, roundingMode);
    }

    public Num add(double val) {
        Num num = new Num(val);
        return add(num);
    }

    public Num add(Num num, int scale) {
        return add(num, scale, roundingMode);
    }

    public Num add(Num num, int scale, int roundingMode) {
        return setDecimal(rounding(this.getDecimal().add(num.getDecimal()), scale, roundingMode));
    }

    public Num sub(Num num) {
        return sub(setOtherNum(num), scale);
    }

    public Num sub(double val) {
        Num num = new Num(val);
        return sub(num);
    }

    public Num sub(Num num, int scale) {
        return sub(num, scale, roundingMode);
    }

    public Num sub(Num num, int scale, int roundingMode) {
        BigDecimal result = this.getDecimal().subtract(num.getDecimal());
        result = rounding(result, scale, roundingMode);
        return setDecimal(result);
    }

    private Num setOtherNum(Num num) {
        num = new Num(num, scale, roundingMode);
        return num;
    }

    public double round(int scale) {
        return rounding(this.decimal, scale, roundingMode).doubleValue();
    }

    public double round(int scale, int roundingMode) {
        return rounding(this.decimal, scale, roundingMode).doubleValue();
    }

    public static BigDecimal rounding(BigDecimal decimal, int scale, int roundingMode) {
        return decimal.divide(one, scale, roundingMode);
    }

    public static BigDecimal rounding(BigDecimal decimal, int scale) {
        return rounding(decimal, scale, BigDecimal.ROUND_HALF_UP);
    }

    public static double rounding(double val, int scale) {
        return rounding(val, scale, BigDecimal.ROUND_HALF_UP);
    }

    public static double rounding(double val, int scale, int roundingMode) {
        return rounding(new BigDecimal(val), scale, roundingMode).doubleValue();
    }

    @Override
    public String toString() {
        return "Num [decimal=" + decimal + ", scale=" + scale + ", roundingMode=" + roundingMode + "]";
    }

}