Chapter 9 Exercise 12 Introduction to Java Programming Tenth

Chapter 9 Exercise 12, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

9.12 (Geometry: intersecting point)
Suppose two line segments intersect. The two end-points for the first line segment
are (x1, y1) and (x2, y2) and for the second line segment are (x3, y3) and (x4, y4).
Write a program that prompts the user to enter these four endpoints and displays the
intersecting point. As discussed in Program- ming Exercise 3.25, the intersecting point can
be found by solving a linear equation. Use the LinearEquation class in Programming Exercise 9.11

this is the code from 9.11

import java.util.Scanner;

public class LinearEquationTest {

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

System.out.println(\"Enter value of a, b, c, d, e and f: \");

int a = sc.nextInt();
int b = sc.nextInt();
int c = sc.nextInt();
int d = sc.nextInt();
int e = sc.nextInt();
int f = sc.nextInt();
  
LinearEquation eqution = new LinearEquation(a, b, c, d, e, f);
  
System.out.println(\"isSolavable: \"+eqution.isSolavable());
System.out.println(\"X: \"+eqution.getX());
System.out.println(\"Y: \"+eqution.getY());
}
}

/*
Sample run:
Enter value of a, b, c, d, e and f:

1
2
3
4
5
6
isSolavable: true
X: -4.0
Y: 4.5
*/
-------------

and

public class LinearEquation {

// instance variables

private int a, b, c, d, e, f;

// constructor

public LinearEquation(int a, int b, int c, int d, int e, int f) {

this.a = a;
this.b = b;
this.c = c;
this.d = d;
this.e = e;
this.f = f;

}

// getters

public int getA() {

return a;

}

public int getB() {

return b;

}

public int getC() {

return c;

}

public int getD() {

return d;

}

public int getE() {

return e;

}

public int getF() {

return f;

}

  

// other functions

public boolean isSolavable(){

if((a*d - b*c) != 0)

return true;

else

return false;

}

  

public double getX(){

if(isSolavable())

return (double)(e*d - b*f)/(double)(a*d - b*c);

else

return -999;

}

  

public double getY(){

if(isSolavable())

return (double)(a*f - e*c)/(double)(a*d - b*c);

else

return -999;

}

}

Solution

import java.util.Scanner;
public class IntersectionPoint {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
   // reading values from user
System.out.println(\"Enter values of first segment: \");
int x1 = sc.nextInt();
int y1 = sc.nextInt();
int x2 = sc.nextInt();
int y2 = sc.nextInt();
   System.out.println(\"Enter values of second segment: \");
int x3 = sc.nextInt();
int y3 = sc.nextInt();
   int x4 = sc.nextInt();
int y4 = sc.nextInt();
     
   //calculating slopes for two lines
   double slope1 = (y2-y1)/(x2-x1);
   double slope2 = (y4-y3)/(x4-x3);
     
   if((slope1 - slope2) == 0){
       System.out.println(\"Lines arenot intersecting..\");
   }
   else{
       // calculating c1, c2 points
       //y = mx+c ==> y-mx
       double c1 = y1-slope1*x1;
       double c2 = y3-slope2*x3;
       // calculating final intersection points
       double intersect1 = (c2-c1)/(slope1-slope2);
       double intersect2 = slope1 * intersect1 + c1;
       System.out.println(\"Intersection points.. x-> \"+intersect1+\", y-> \"+intersect2);
   }
}
}