Java BigDecimal Square Root sqrt(BigDecimal number, RoundingMode rounding)

Description

sqrt

License

Apache License

Declaration

public static BigDecimal sqrt(BigDecimal number, RoundingMode rounding) 

Method Source Code

//package com.java2s;
/***************************************************************************
 * Copyright (c) 2016 the WESSBAS project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License./*from w  w  w  .  j  av a2  s  . c  o m*/
 ***************************************************************************/

import java.math.BigDecimal;
import java.math.BigInteger;
import java.math.RoundingMode;

public class Main {
    protected static BigInteger BigIntegerZERO = BigInteger.ZERO;
    protected static BigInteger BigIntegerONE = BigInteger.ONE;
    protected static BigInteger BigIntegerTWO = BigInteger.valueOf(2);
    protected static BigDecimal BigDecimalZERO = BigDecimal.ZERO;
    protected static BigDecimal BigDecimalONE = BigDecimal.ONE;
    protected static BigDecimal BigDecimalTWO = new BigDecimal(2);

    public static BigInteger sqrt(BigInteger number) {
        return sqrt(number, BigIntegerONE);
    }

    public static BigDecimal sqrt(BigDecimal number, RoundingMode rounding) {
        return sqrt(number, BigDecimalONE, rounding);
    }

    protected static BigInteger sqrt(BigInteger number, BigInteger guess) {
        // ((n/g) + g)/2: until same result twice in a row
        //    BigInteger result = number.divide(guess).add(guess).divide(BigIntegerTWO);
        //    if(result.compareTo(guess) == 0)
        //      return result;
        //
        //    return sqrt(number, result);

        // redoing this to avoid StackOverFlow
        BigInteger result = BigIntegerZERO;
        BigInteger flipA = result;
        BigInteger flipB = result;
        boolean first = true;
        while (result.compareTo(guess) != 0) {
            if (!first)
                guess = result;
            else
                first = false;

            result = number.divide(guess).add(guess).divide(BigIntegerTWO);
            // handle flip flops
            if (result.equals(flipB))
                return flipA;

            flipB = flipA;
            flipA = result;
        }
        return result;

    }

    public static BigDecimal sqrt(BigDecimal number, BigDecimal guess, RoundingMode rounding) {
        BigDecimal result = BigDecimalZERO;
        BigDecimal flipA = result;
        BigDecimal flipB = result;
        boolean first = true;
        while (result.compareTo(guess) != 0) {
            if (!first)
                guess = result;
            else
                first = false;

            result = number.divide(guess, rounding).add(guess).divide(BigDecimalTWO, rounding);
            // handle flip flops
            if (result.equals(flipB))
                return flipA;

            flipB = flipA;
            flipA = result;
        }
        return result;
    }
}

Related

1. sqrt(BigDecimal number)
2. sqrt(BigDecimal original, int scale)
3. sqrt(BigDecimal randicand)
4. sqrt(BigDecimal value)
5. sqrt(BigDecimal value, int decimalPlaces)