How to convert double x1 = input.nextDouble(); into an array?

Question

/*
(Geometry: area of a triangle) Write a program that prompts the user to enter
three points (x1, y1), (x2, y2), (x3, y3) of a triangle and displays its area.
*/
import java.util.Scanner;

public class Exercise_02_19 {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        // Prompt the user to enter three points
        System.out.print("Enter three points for a triangle: ");
        double x1 = input.nextDouble();
        double y1 = input.nextDouble();
        double x2 = input.nextDouble();
        double y2 = input.nextDouble();
        double x3 = input.nextDouble();
        double y3 = input.nextDouble();

        // Compute the area of a triangle
        double side1 = Math.pow(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2), 0.5);
        double side2 = Math.pow(Math.pow(x3 - x2, 2) + Math.pow(y3 - y2, 2), 0.5);
        double side3 = Math.pow(Math.pow(x1 - x3, 2) + Math.pow(y1 - y3, 2), 0.5);
        double s = (side1 + side2 + side3) / 2;
        double area = Math.pow(s * (s - side1) * (s - side2) * (s - side3), 0.5);

        // Display result
        System.out.println("The area of the triangle is " + area);
    }
}

I am learning the Java coding language and currently stuck on a question. How can I convert double x1 = input.nextDouble(); into an array that does x1 to 3 and y1 to 3? We are currently using the Introduction to Java Programming and Data Structures Twelfth Edition and even taking the time to read and understand what is going on is hard for me to comprehend. If there is someone with Java knowledge to help what went wrong and point me in the right direction that would be great. Thank you!

What does _that does x1 to 3 and y1 to 3_ mean? – Sotirios Delimanolis Sep 13 '21 at 18:14 — Sotirios Delimanolis, Sep 13 '21 at 18:14
OP meant to write x1 to x3 and y1 to y3 – Abishek Stephen Sep 13 '21 at 18:23 — Abishek Stephen, Sep 13 '21 at 18:23

score 1 · Accepted Answer · answered Sep 13 '21 at 18:02

1

double[] x = new double[3];
double[] y = new double[3];

Now you can access x1 to x3 as x[0] to x[2] and similarly for y.

answered Sep 13 '21 at 18:02

Abishek Stephen

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Thank you for this. I am just having one more problem, I added this into the java file but now the x2 in the file is saying: `The local variable x1 may not have been initialized` how can I fix this when it's an array? – zucc0nit Sep 13 '21 at 19:37
1

Change x1 to x[0], x2 to x[1] and x3 to x[2]. What we have done is replace x1, x2 and x3 to the array values of x[0], x[1] and x[2]. Do the same for "y" also. – Abishek Stephen Sep 13 '21 at 19:41
Abishek, how can I still ask for user input then give the output of the triangle? Before I used the array's the program worked but now it's not. How can I fix it? – zucc0nit Sep 13 '21 at 20:09
Share what error it is showing. I can't help if you do not share the error specifically. – Abishek Stephen Sep 13 '21 at 20:11
There is no error, it just shows this: https://i.imgur.com/408e8I7.png No output. – zucc0nit Sep 13 '21 at 20:29
You have removed the part where you read the value with input.nextDouble() then the value will not be set right? When I said change x1 to x[0] you deleted the part where the value is input. Do you get my point? – Abishek Stephen Sep 13 '21 at 20:34
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/237066/discussion-between-zucc0nit-and-abishek-stephen). – zucc0nit Sep 13 '21 at 20:37

How to convert double x1 = input.nextDouble(); into an array?

1 Answers1