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Distance between coordinates in Java

I'm trying to solve this problem.
Determine the distance between point (x1, y1) and point (x2, y2), and assign the result to pointsDistance.
I'll now present the original code along with my answer to the problem:
import java.util.Scanner;
public class CoordinateGeometry {
public static void main(String[] args) {
Scanner scnr = new Scanner(System.in);
double x1;
double y1;
double x2;
double y2;
double pointsDistance;
double xDist;
double yDist;
pointsDistance = 0.0;
xDist = 0.0;
yDist = 0.0;
x1 = scnr.nextDouble();
y1 = scnr.nextDouble();
x2 = scnr.nextDouble();
y2 = scnr.nextDouble();
pointsDistance = Math.sqrt(x2 - Math.pow(x1, 2) + y2 - Math.pow(y1, 2)); //*Learning Square Rooots and powers*//
System.out.println(pointsDistance);
}
}
The desired outcomes from the inputs are not printing. For an example:
My value:
1
Expected value:
3
Where have I gone wrong?

Your formula is incorrect. It should be:
pointsDistance = Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));
This is just an application of the Pythagorean theorem, and Java has a Math.hypot() convenience method that also protects against arithmetic overflow/underflow:
pointsDistance = Math.hypot(x2-x1, y2-y1);
Thanks to #LouisWasserman for the helpful comment.

Method from other class and use of toString()

I am trying to make this code work, receive 2 points (x, y) & (x1,y1) from user on MAIN and use a method from another class and get the calculation.
Also it would be very nice to receive an explanation about toString.
import java.util.Scanner;
public class Test{
public static void main(String[]args)
{
Scanner scan = new Scanner(System.in);
double x , y , x1 , y1;
Pytaguras Triangle = new Pytaguras();
System.out.println("Hello , this program is using Pytagoras formula" +
" on the 4 point that you enter");
System.out.println("Please enter 4 points to calculate the distance");
x = scan.nextDouble();
y = scan.nextDouble();
x1 = scan.nextDouble();
y1 = scan.nextDouble();
Triangle.setDouble( x, y, x1, y1);
System.out.println("the distance between 2 points is :" + Triangle.calculate() );
}
}
public class Pytaguras
{
private double x, y, x1 ,y1 ;
public void setDouble(double _x, double _y, double _x1, double _y1)
{ _x=x;
_y=y;
_x1=x1;
_y1=y1;}
public double calculate(double _x , double _y , double _x1 , double _y1 )
{ double s;
s = Math.sqrt((_x-_y)*(_x-_y)+(_x1-_y1)*(_x1-_y1));
return s;
}
}

If you would like to receive the distance-calculation via method toString() of your class Triangle, you just need to implement it same like method calculate:
Possible solution using toString
Your class would look like this:
public class Pytaguras {
private double x, y, x1 ,y1 ;
public void setDouble(double _x, double _y, double _x1, double _y1) {
_x=x;
_y=y;
_x1=x1;
_y1=y1;
}
public static double calculate(double _x , double _y , double _x1 , double _y1 ) {
return Math.sqrt((_x-_y)*(_x-_y)+(_x1-_y1)*(_x1-_y1));
}
public String toString() {
return "Distance is " + Math.sqrt((x - y)*(x -y)+(x1 - y1)*(x1 - y1));
}
}
What probably went wrong?
When you tried to implement toString() like this:
// code omitted for clarity
public double calculate(double _x , double _y , double _x1 , double _y1 ) {
double s; // variable declared locally, thus can be used only inside this method
s = Math.sqrt((_x-_y)*(_x-_y)+(_x1-_y1)*(_x1-_y1));
return s;
}
// code omitted for clarity
public String toString() {
return s; // will give compiler-error, since symbol/variable "s" is not visible here, but only inside method calculate
}
// code omitted for clarity
Refactoring = optimizing your code
use static on utility-method : Your calculation method does not depend on any variables (x,y,x1,y1) declared inside the class, but on parameters only. So it is independent and can be made static. Thus would make it a utility-method that can be called from outside like Pytaguras.calculate(...). See Java Tutorial on static.
use constructor for initialization of variables: Your 2 points can be directly initialized by using a constructor. Thus you do not need to call both new Pytaguras() and setDouble(x1, y1, x2, y2). You could simply call new Pytaguras(x1, y1, x2, y2). See Java Tutorial on constructor.

You can simply assign the values through the class constructor.
public class Triangle {
private double x, y, x1 , y1;
public Triangle(double new_x, double new_y, double new_x1, double new_y1) {
x = new_x;
y = new_y;
x1 = new_x1;
y1 = new_y1;
}
public double calculate() {
return Math.sqrt((x-y)*(x-y)+(x1-y1)*(x1-y1));
}
}
And then on your main:
public static void main(String[]args) {
Scanner scan = new Scanner(System.in);
double x , y , x1 , y1;
Pytaguras Triangle = new Pytaguras();
System.out.println("Hello , this program is using Pytagoras formula" +
" on the 4 point that you enter");
System.out.println("Please enter 4 points to calculate the distance");
x = scan.nextDouble();
y = scan.nextDouble();
x1 = scan.nextDouble();
y1 = scan.nextDouble();
Triangle triangle = new Triangle(x, y, x1, y1);
System.out.println("the distance between 2 points is :" + triangle.calculate());
}

Finding length and angles of a triangle

My job is to compute the following properties of a given triangle: lengths of all sides, angles at all corners, the perimeter and the area. I have a Triangle class and a Triangle tester class. I THINK I have coded the perimeter and area correctly? But I am beginning to think instead of setting a constant variable side for my perimeter I should be using the lengths of all sides to find my perimeter as well. What I am stuck on is finding the lengths and the angles. For some reason when I run my tester class they all come out as 1.0. Any advice would be appreciated! Thank you!
import java.util.Scanner;
public class Triangle
{
Scanner in = new Scanner(System.in);
/**
* Variables
*/
double x1;
double x2;
double x3;
double y1;
double y2;
double y3;
double lengthA;
double lengthB;
double lengthC;
double angleA;
double angleB;
double angleC;
double area;
double perimeter;
double base;
double height;
double p;
/**
Constructs x and y coordinates
#param x1, x2, x3 to x1, x2, x3
#param y1, y2, y3 to y1, y2, y3
*/
public Triangle(double x1, double x2, double x3, double y1, double y2, double y3)
{
this.x1 = x1;
this.x2 = x2;
this.x3 = x3;
this.y1 = y1;
this.y2 = y2;
this.y3 = y3;
}
/**
*Find lengths of all sides
*/
public double getLengthA()
{
lengthA = Math.sqrt(Math.pow((x2 - x1), 2) + Math.pow((y2 - y1), 2));
return lengthA;
}
public double getLengthB()
{
lengthB = Math.sqrt(Math.pow((x3 - x2), 2) + Math.pow((y3 - y2), 2));
return lengthB;
}
public double getLengthC()
{
lengthC = Math.sqrt(Math.pow((x1 - x3), 2) + Math.pow((y1 - y3), 2));
return lengthC;
}
/**
* Find angles at all corners
#return angles at all corners
*/
public double getAngleA()
{
angleA = lengthA + lengthB + lengthC - (lengthB * lengthC);
return angleA;
}
public double getAngleB()
{
angleB = lengthB + lengthA + lengthC - (lengthA * lengthC);
return angleB;
}
public double getAngleC()
{
angleC = lengthC + lengthA + lengthB - (lengthA * lengthB);
return angleC;
}
/**
* Constant Variables
*/
public Triangle()
{
base = 5;
height = 15;
}
/**
* Find perimeter of triangle
*/
public double getPerimeter()
{
perimeter = lengthA + lengthB + lengthC;
return perimeter;
}
public double getHalfPerimeter()
{
p = perimeter / 2;
return p;
}
/**
* Find area of triangle
*/
public double getArea()
{
double area = Math.sqrt(p * (p - lengthA) * (p - lengthB) * (p - lengthC));
return area;
}
}
Here is my tester class:
import java.util.Scanner;
import javax.swing.JOptionPane;
public class TriangleSimulator
{
public static void main (String[] args)
{
Scanner in = new Scanner(System.in);
String input = JOptionPane.showInputDialog("Enter X coordinate for the first corner of the triangle: ");
double x1 = Double.parseDouble(input);
input = JOptionPane.showInputDialog("Enter Y coordinate for the first corner of the triangle: ");
double y1 = Double.parseDouble(input);
input = JOptionPane.showInputDialog("Enter X coordinate for the second corner of the triangle: ");
double x2 = Double.parseDouble(input);
input = JOptionPane.showInputDialog("Enter Y coordinate for the second corner of the triangle: ");
double y2 = Double.parseDouble(input);
input = JOptionPane.showInputDialog("Enter X coordinate for the third corner of the triangle: ");
double x3 = Double.parseDouble(input);
input = JOptionPane.showInputDialog("Enter Y coordinate for the third corner of the triangle: ");
double y3 = Double.parseDouble(input);
Triangle t = new Triangle(x1, x2, x3, y1, y2, y3);
System.out.println("Length A is: " + t.getLengthA());
System.out.println("Length B is: " + t.getLengthB());
System.out.println("Length C is: " + t.getLengthC());
System.out.println("Angle A is: " + t.getAngleA());
System.out.println("Angle B is: " + t.getAngleB());
System.out.println("Angle C is: " + t.getAngleC());
System.out.println("Area: " + t.getArea());
System.out.println("Perimeter: " + t.getPerimeter());
in.close();
}
}

You're showing JOptionPanes that prompt the user for input, but you're not getting the input and you're thus not using the input to set the state of your Triangle, creating a default Triangle object using its parameterless constructor. Understand that there's no magic in Java programming, and your Triangle object will not magically know what numbers the user has entered and change itself accordingly. Instead you must give that information into your Triangle.
What you must do is assign the results returned from the JOptionPanes, parse them into doubles, and then use those numbers to create a Triangle, using the constructor that takes numeric value parameters, not the default constructor. Do this, and you should be good.
e.g.
String input = JOptionPane.showInputDialog("Enter X coordinate for the first corner of the triangle: ");
double x1 = Double.parseDouble(input);
input = JOptionPane.showInputDialog("Enter Y coordinate for the first corner of the triangle:
double y1 = Double.parseDouble(input);
//.... etc repeat...
Triangle triangle = new Triangle(x1, x2, x3, y1, y2, y3);
Edit
This constructor ignores the values being passed in:
public Triangle(double x1, double x2, double x3, double y1, double y2, double y3)
{
x1 = 0;
x2 = 0;
x3 = 0;
y1 = 0;
y2 = 0;
y3 = 0;
}
A constructor like the one you'll need, should take the values passed in, and use those values to set class fields. For instance here:
public class Foo {
private int bar; // the bar field
public Foo(int bar) {
this.bar = bar;
}
}
Note that I use this.bar above so that Java knows that I want to set the bar field with the value held by the bar parameter (the bar without the this). You will need to do something similar only with 6 parameters, not one.
Then you do all your calculations in a separate block of code called an initializer block:
{
/**
* Find lengths of all sides
*/
lengthA = Math.pow(Math.pow((x2 - x1), 2) + Math.pow((y2 - y1), 2) * .05, lengthA);
lengthB = Math.pow(Math.pow((x3 - x2), 2) + Math.pow((y3 - y2), 2) * .05, lengthB);
lengthC = Math.pow(Math.pow((x1 - x3), 2) + Math.pow((y1 - y3), 2) * .05, lengthC);
}
This code gets called before your constructor, and so even if you set your Triangles fields correctly, this code wouldn't work. You don't want to use initializer blocks, and you can forget I even mentioned them other than to tell you not to use them. Instead do your calculations inside your constructor, and do so after setting all your fields.
Note that I've purposely not posted a solution to your problem because I firmly believe that what most of us need is to understand the concepts underlying any problems we are having, and then use that understanding to create our own code solutions.
Most important, read your texts, no better, study your texts, because the mistakes you're making involve foundational concepts, and show that you don't yet understand these concepts and have resorted to guessing. This will never work, as you need to understand all this and understand it well if you're going to be able to progress in this course.
Good luck!
Edit 2
For Tom, run this:
public class TestInitializerBlock {
public TestInitializerBlock() {
System.out.println("Inside of constructor");
}
{
System.out.println("Inside of initializer block");
}
public static void main(String[] args) {
new TestInitializerBlock();
}
}

How do I properly fix my function calling (java)?

This is just a small portion of the code, since I feel like it would be enough to get my point across.
public class Line {
private double x1;
private double x2;
private double y1;
private double y2;
public Project2(double a,double b,double c,double d) {
x1 = a;
x2 = b;
y1 = c;
y2 = d;
}
public double length () { //the length of a line
double step1 = Math.pow((x1-x2),2);
double step2 = Math.pow((y1-y2),2);
double step3 = step1+step2;
double step4 = Math.sqrt(step3);
return step4;}}
import java.util.Scanner;
public class Project2Main {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Enter starting coordinates for a line (starting with x then y): ");
double a = input.nextInt();
double b = input.nextInt();
System.out.println("Enter ending coordinates for the line (starting with x then y): ");
double c = input.nextInt();
double d = input.nextInt();
Line line1 = new Line(a,b,c,d);
System.out.println("The length of the line is: " + line1.length());
Whenever I try to run it, it just gives length of the line as 0.0.
At first I tried to pass line1 as an argument, but then I realized that I couldn't (or at least didn't know how to) call it since I couldn't do Line.length(line1) or line1.length(line1).

You state:
I tried with just a simple 1,1 and 2,2. Expected output was 1.41, what I got was 0.0
You're confusing the order of parameters in your method. Your method lists x1, x2, y1, y2, and with this, 1, 1, 2, 2, will check the length of line from point 1, 2 to 1, 2 which is 0.0. I think that you want to change your parameter order to x1, y1, x2, y2.
In fact, you should clarify your parameter variables to make them self commenting. Get rid of a, b, c, d and change to: x1, y1, x2, y2:
public class Line {
// order changed
private double x1;
private double y1;
private double x2;
private double y2;
// parameter names clarified and order changed
public Project2(double x1, double y1, double x2, double y2) {
this.x1 = x1;
this.y1 = y1;
this.x2 = x2;
this.y2 = y2;
}

Triangle class using an abstract shape class

So I have this triangle class I need to create using an abstract class. It will also be drawn by a tester class. I am part of the way through it but I am having serious issues with the math portion. I have set the coordinates in the tester class, I have no idea of how to get the pen to turn a certain degree to draw the next side of the triangle. Attached is all the classes and I have so far. Any help will be appreciated.
Tester class
import TurtleGraphics.*;
public class TestShapes1 {
public static void main (String[] args) {
// Declare and instantiate a pen, a circle and a wheel
Pen p = new StandardPen();
//Shape s1 = new Circle1 (20, 20, 20);
//Shape s2 = new Wheel1 (-20, -20, 20, 6);
Shape1 t2 = new Triangle1 (0, 0, 50, 0, 0, 30);
// Draw the circle and wheel
//s1.draw (p);
t2.draw (p);
}
}
Shape Class
import TurtleGraphics.Pen;
public interface Shape1 {
public double area();
public void draw (Pen p);
public double getXPos();
public double getYPos();
public void move (double xLoc, double yLoc);
public void stretchBy (double factor);
public String toString();
}
Triangle Class
import TurtleGraphics.Pen;
public class Triangle1 implements Shape1 {
private double x1, y1, x2, y2, x3, y3;
private double s1, s2, s3;
private double d1, d2;
//private double height, width;
public Triangle1() {
x1 = 0;
y1 = 0;
x2 = 1;
y2 = 0;
x3 = 0;
y3 = 1;
//height = 1;
//width = 1;
}
public Triangle1 (double xLoc1, double yLoc1, double xLoc2, double yLoc2, double xLoc3, double yLoc3) {
x1 = xLoc1;
y1 = yLoc1;
x2 = xLoc2;
y2 = yLoc2;
x3 = xLoc3;
y3 = yLoc3;
//height = h;
//width = w;
}
public double area() {
return (Math.abs(x1*y2-x2*y1+x2*y3-x3*y2+x3*y1-x1*y3))/2.0;
}
public void draw (Pen p) {
s1 = Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
s2 = Math.sqrt((x2-x3)*(x2-x3)+(y2-y3)*(y2-y3));
s3 = Math.sqrt((x3-x1)*(x3-x1)+(y3-y1)*(y3-y1));
p.up();
p.move (x1, y1);
p.down();
p.setDirection (0);
p.move (s1);
d1 = (Math.acos((s2*s2+s3*s3-s1*s1)/(2.0*s2*s3)))*180/Math.PI;
p.turn (180 - d1);
p.move (s2);
d2 = (Math.acos((s3*s3+s1*s1-s2*s2)/(2.0*s3*s1)))*180/Math.PI;
p.turn (180 - d2);
p.move (s3);
p.turn (-90);
//p.move ();
}
public double getXPos() {
return x1;
}
public double getYPos() {
return y1;
}
public void move (double xLoc, double yLoc) {
x1 = x1 + xLoc;
y1 = y1 + yLoc;
x2 = x2 + xLoc;
y2 = y2 + yLoc;
x3 = x3 + xLoc;
y3 = y3 + yLoc;
}
public void stretchBy (double factor) {
x1 *= factor;
y1 *= factor;
}
public String toString() {
String str = "TRIANGLE\n";
// + "Width & Height: " + width + " & " + height +"\n"
// + "(X,Y) Position: (" + xPos + "," + yPos + ")\n"
// + "Area: " + area();
return str;
}
}

You don't need any math. Just pass the degrees to p.turn(). So use
p.turn(180);
instead of
d1 = (Math.acos((s2*s2+s3*s3-s1*s1)/(2.0*s2*s3)))*180/Math.PI;
p.turn (180 - d1);
See the documentation for reference:
The degrees can be an integer or floating-point number. Example:
pen.turn(-45); Rotate the pen 45 degrees clockwise.