Java開平方根代碼——牛頓迭代法

使用牛頓迭代法，代碼如下：

package project.test;

import java.math.*;


public class SqrtTest {
private static final String num = "10";
private static final int accuracy = 5;
private static double accuracyDouble = 0.1;


public static void main(String[] args) {
calSqrt();
}


private static void calSqrt() {
BigDecimal guessNum = new BigDecimal(1);
for (int i = 0; i < accuracy; i++) {
accuracyDouble *= 0.1;
}
while (true) {
BigDecimal temp = SqrtTest.newtonMethod(guessNum);
if (temp.equals(guessNum)) {
break;
}
double d = guessNum.subtract(temp).doubleValue();
if (d > 0 && d < accuracyDouble) {
guessNum = temp;
break;
}
guessNum = temp;
}
System.out.println("Result is " + guessNum);
}


private static BigDecimal newtonMethod(BigDecimal guessNum) {
return guessNum.subtract((guessNum.multiply(guessNum).subtract(new BigDecimal(num))).divide(new BigDecimal(2).multiply(guessNum), accuracy, BigDecimal.ROUND_HALF_EVEN));
}


}