Java BigDecimal Power pow(BigDecimal arg0, BigDecimal arg1)

Description

pow

License

Mozilla Public License

Declaration

static BigDecimal pow(BigDecimal arg0, BigDecimal arg1) 

Method Source Code

//package com.java2s;
/** This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *///from ww  w  .  ja va  2 s .  c o m

import java.math.*;

public class Main {
    private static final MathContext MC_100 = new MathContext(100, RoundingMode.HALF_UP);

    static BigDecimal pow(BigDecimal arg0, BigDecimal arg1) {
        try {
            //check if arg1 (power) is an integer
            BigInteger bi = arg1.toBigIntegerExact();
            return arg0.pow(bi.intValue(), MC_100);
        } catch (ArithmeticException ex) {
            //arg1 is not an integer
            int n = arg1.intValue();
            switch (arg1.signum()) {
            case 0: //=0
                if (arg0.compareTo(BigDecimal.ZERO) != 0) {
                    return new BigDecimal(1);
                } else
                    throw new ArithmeticException("Invalid calculation: 0 ^ 0");

            case 1: //>0
            {
                BigDecimal result = arg0.pow(n);
                double x = Math.pow(arg0.doubleValue(), arg1.doubleValue() - n);
                if ((new Double(x).equals(Double.NaN))
                        || (new Double(Math.abs(x)).equals(Double.POSITIVE_INFINITY))) {
                    throw new ArithmeticException("too large result");
                } else {
                    return result.multiply(BigDecimal.valueOf(x));
                }
            }

            case -1: //<0
            {
                //n<0, so -n>0
                //e.g. 2.2^(-2.1)
                //now n=-2, result=(2.2^-2)*(2.2*-0.1)=(2.2*-0.1)/(2.2^2)
                BigDecimal result = arg0.pow(-n);
                double x = Math.pow(arg0.doubleValue(), arg1.doubleValue() - n);
                if ((new Double(x).equals(Double.NaN))
                        || (new Double(Math.abs(x)).equals(Double.POSITIVE_INFINITY))) {
                    throw new ArithmeticException("too large result");
                } else {
                    return BigDecimal.valueOf(x).divide(result, MC_100);
                }
            }

            default: //cannot happen
                throw new Error();
            }
        }
    }
}

Related

1. decimalPow(BigDecimal number, BigDecimal power)
2. pow(BigDecimal b, int p, int q)
3. pow(BigDecimal base, BigDecimal exponent)
4. pow(BigDecimal base, BigDecimal power)
5. pow(BigDecimal one, int another)