Java BigDecimal Square Root sqrt(BigDecimal value, int decimalPlaces)

Description

sqrt

License

Open Source License

Parameter

Parameter	Description
value	a parameter
decimalPlaces	a parameter

Declaration

public static BigDecimal sqrt(BigDecimal value, int decimalPlaces) 

Method Source Code

//package com.java2s;
/*//w w w .j  ava 2s.c o  m
 * Utility class to simplify the use of BigDecimals
 * Copyright (C) 2012 Martin Absmeier, IT Consulting Services
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

import java.math.BigDecimal;

import java.math.MathContext;
import java.math.RoundingMode;

public class Main {
    /**
     * 
     * @param value
     * @param decimalPlaces
     * @return
     */
    public static BigDecimal sqrt(BigDecimal value, int decimalPlaces) {
        BigDecimal zero = BigDecimal.ZERO.setScale(decimalPlaces + 10);
        BigDecimal one = BigDecimal.ONE.setScale(decimalPlaces + 10);
        BigDecimal two = new BigDecimal("2").setScale(decimalPlaces + 10);
        BigDecimal maxerr = one.movePointLeft(decimalPlaces);
        BigDecimal lower = zero;
        BigDecimal upper = value.compareTo(one) <= 0 ? one : value;
        BigDecimal mid = BigDecimal.ZERO;

        while (true) {
            mid = lower.add(upper).divide(two);
            // mid = lower.add(upper).divide(two, RoundingMode.HALF_UP);
            BigDecimal sqr = mid.multiply(mid);
            BigDecimal error = value.subtract(sqr).abs();
            if (error.compareTo(maxerr) <= 0) {
                break;
            }
            if (sqr.compareTo(value) < 0) {
                lower = mid;
            } else {
                upper = mid;
            }
        }

        return mid.round(getMathContext(decimalPlaces));
    }

    private static MathContext getMathContext(int decimalPlaces) {
        return new MathContext(decimalPlaces, RoundingMode.HALF_UP);
    }
}

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2. sqrt(BigDecimal number, RoundingMode rounding)
3. sqrt(BigDecimal original, int scale)
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