圆周率的求出如何用Java实现

Question

请给出编程语句,结果精确到小数点后100位
谢谢指点

Answer 1

如果你真的想要那样的精度，请执行下面的程序，再等上几个小时
import java.math.*;
public class ForPI {

//PI=4*(1-1/3+1/5-1/7...)
public static String forPI(int a){

BigDecimal result,index,temp,flag,b,c;
b=new BigDecimal(1,new MathContext(a,RoundingMode.HALF_UP));//分子
c=new BigDecimal(2);//增量
result=new BigDecimal(0,new MathContext(a,RoundingMode.HALF_UP));
index=new BigDecimal(1);//分母
temp=new BigDecimal(1,new MathContext(a,RoundingMode.HALF_UP));
flag=new BigDecimal(0.1);
flag=flag.pow(a);//精度
while(temp.abs().compareTo(flag)==1){
temp=b.divide(index);
result.add(temp);
index.add(c);
index=index.negate();
}
result=result.multiply(new BigDecimal(4));
return result.toPlainString();

}

public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println(forPI(100));

}

}