java编程求一元三次方程a*x*x*x+b*x*x+c*x+d=0的根

import java.io.*;
public class Test1
{
public static void main(String[] args) throws IOException
{
double a,b,c,d,x,y;
System.out.println("一元三次方程求解:y=ax3+bx2+cx+d");
System.out.println("请输入a值:");
BufferedReader in1=new BufferedReader(new InputStreamReader(System.in));
a=Double.parseDouble(in1.readLine());
System.out.println("请输入b值:");
BufferedReader in2=new BufferedReader(new InputStreamReader(System.in));
b=Double.parseDouble(in2.readLine());
System.out.println("请输入c值:");
BufferedReader in3=new BufferedReader(new InputStreamReader(System.in));
c=Double.parseDouble(in3.readLine());
System.out.println("请输入d值:");
BufferedReader in4=new BufferedReader(new InputStreamReader(System.in));
d=Double.parseDouble(in4.readLine());
System.out.println("请输入x值:");
BufferedReader in5=new BufferedReader(new