求解哈，请问这一句哪错了。

Question

import java.io.*;
import java.math.*;
public class xianduan extends jisuan
{

public static void main(String args[])
{

try{

BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
System.out.println("输入X1");
x1=Integer.parseInt(br.readLine());
System.out.println("输入Y1");
y1=Integer.parseInt(br.readLine());
System.out.println("输入X2");
x2=Integer.parseInt(br.readLine());
System.out.println("输入Y2");
y2=Integer.parseInt(br.readLine());
}catch(IOException e){}
jisuan L=new jisuan(x1,x2,y1,y2);
L.cs();
}
}

class jisuan
{
static int x1,x2,y1,y2;
public jisuan(){}

jisuan(int x1,int x2, int y1,int y2)
{this.x1=x1;
this.x2=x2;
this.y1=y1;
this.y2=y2;
}
public void cs(){
double length;
length=sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
System.out.println("线段长度为 "+length);
}
}
length=sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));

Answer 1

Math.sqrt