Here you can find the source of sqrt(BigDecimal original, int scale)
public static BigDecimal sqrt(BigDecimal original, int scale)
//package com.java2s; /*//from w w w .j a v a 2s. co m Copyright 2015 HJOW 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. */ import java.math.BigDecimal; public class Main { public static BigDecimal sqrt(BigDecimal original, int scale) { BigDecimal temp = new BigDecimal(String.valueOf(original)); BigDecimal results = new BigDecimal("1.0"); results.setScale(scale + 2); int loops = 0; while (true) { if (loops >= 1) { temp = new BigDecimal(String.valueOf(results)); } temp.setScale(scale + 2, BigDecimal.ROUND_FLOOR); results = original.divide(temp, scale + 2, BigDecimal.ROUND_FLOOR).add(temp) .divide(new BigDecimal("2.0"), scale + 2, BigDecimal.ROUND_FLOOR); if (temp.equals(results)) break; loops++; } return results.setScale(scale, BigDecimal.ROUND_HALF_UP); } }