### Lines.java

import java.util.Scanner;
/**
This program reads in four double variables, x1, y1, x2, and y2,
which represent the end points of a line segments, namely,
x1 is the x-coordinate of the starting point,
y1 is the y-coordinate of the starting point,
x2 is the x-coordinate of the ending point, and
y2 is the y-coordinate of the ending point.
The length of the line segment joining (x1, y1) and (x2, y2)
is computed using the Pythagorean theorem.
*/
public class Lines
{
public static void main (String[] args)
{
// Read coordinates
Scanner in = new Scanner(System.in);
double x1 = in.nextDouble();
double y1 = in.nextDouble();
double x2 = in.nextDouble();
double y2 = in.nextDouble();
// Compute and print out the length of the line segment
// Your work here
...
System.out.println(length);
}
}