2.15
import java.util.Scanner;
public class Demo_1{
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.print("输入 x1 和y1: ");
System.out.print("输入 x2 和 y2: ");
double b=input.nextDouble();
double d=input.nextDouble();
double a=input.nextDouble();
double c=input.nextDouble();
double y= (b-a)*(b-a)+(d-c)*(d-c);
double distance = Math.pow(y, 0.5);
System.out.print("The distance the two points is " + distance);
}
}