roots.java

JAVA语言课程学习中的一个程序

import java.io.*;
import java.util.*;
public class roots{
double a,b,c;
double x1,x2,y1,y2;
private double getpara()  //读出输入的数字
{
  byte buf[]=new byte[256];
  double m=0;String str;
  try{
  System.in.read(buf);
  str=new String (buf);
  m=Double.parseDouble(str.trim());
  } catch(Exception e){}
  return m;
}

private void set3para(){
System.out.println("please input the paramter a");
a=getpara();
System.out.println("please input the paramter b");
b=getpara();
System.out.println("please input the paramter c");
c=getpara();
}
private void result(){    //算出一元二次方程的根
double check;
check=b*b-4*a*c;
if(check==0){
x1=(-b)/(2*a);
x2=x1;
}
else
if(check>0){
x1=(-b+(float)Math.sqrt(check))/(2*a);
x2=(-b-(float)Math.sqrt(check))/(2*a);
System.out.println("x1="+x1);
System.out.println("x2="+x2);
}
else
if(check<0){
double check1=-check;
y1=(float)Math.sqrt(check1)/(2*a);
y2=(float)Math.sqrt(check1)/(2*a);
x1=(-b)/(2*a);
x2=x1;
System.out.println("x1="+x1+"+"+y1+"i");
System.out.println("x2="+x2+"-"+y2+"i");
}
}
public static void main(String args[]){  //主函数
roots r=new roots();
r.set3para();
r.result();
}
}