Triangle Analysis in Java

Question

I want to prompt a user for 3 sides to a triangle. Then figure out whether the triangle is a right triangle, equilateral, or isosceles. But I my program just catches an error in the error handling and exits the program when trying to get side(1). So my question is do you see what is causing this or what is wrong with my code?

driver program TestTriangle.java

public class TestTriangle { 
  public static void main(String[] args) {
    System.out.println("Welcome to the Triangle Program");
    System.out.println();

    Triangle myTriangle = new Triangle();
    myTriangle.buildTriangle();

    System.out.println();
    System.out.println("My analysis of this triangle is");
    System.out.println();

    myTriangle.classifyTriangle();

    String prettyPerim = String.format("%.3g", myTriangle.perimeter());
    String prettyArea = String.format("%.3g", myTriangle.area());

    System.out.println("\tThe area of the triangle is " + prettyArea + ".");
    System.out.println("\tThe perimeter of the triangle is " + prettyPerim + ".");
   }
}

program Triangle.java

import java.util.Scanner;
import java.util.InputMismatchException;

public class Triangle {
  public static final double TOLERANCE = 0.0001;

  private double min;
  private double mid;
  private double max;  
  private Scanner input;

  public Triangle() {
    double side1 = 0.0, side2 = 0.0, side3 = 0.0;
  }

  public void buildTriangle() {
    double side1 = getSide(1);
    double side2 = getSide(2);
    double side3 = getSide(3);

    // if side1 is greater than side2, the min is side1 and the max is side2
    if (side1 < side2) {
      min = side1;
      max = side2;
    // otherwise the min is side2 and the max is side1
    } else {
      min = side2;
      max = side1;
    }

    // if side3 is less than the min value, then the mid value is the min value and the min value is side3
    if (side3 < min) {
      mid = min;
      min = side3;
    // if side3 is greater than the max value then the mid is the max and the max is side3
    } else if (side3 > max) {
      mid = max;
      max = side3;
    // otherwise the mid is side3
    } else {
      mid = side3;
    }
  }

  public double getSide(int index) {
    System.out.print("Please enter the length of side " + index + ": ");
    double sideVal = 0.0;
    try{
      sideVal = input.nextDouble();
    } catch (Exception e) {
      System.out.println("You did not enter a valid input. Exiting.");
      System.exit(1);
    }
    return sideVal;
  }

  public void classifyTriangle() {
    // if the max value is greater than the min and the mid combined it is not a triangle, exit the program.
    if (max > min + mid) {
      System.out.println("Not a triangle");
      System.exit(1);
    }
    else if (((Math.pow(min, 2)) + (Math.pow(mid, 2))) == (Math.pow(max, 2))) {      
      System.out.println("This is a right triangle");
    }
    else if (max == min || min == mid || max == mid) {
      if (max == min && min == mid && max == mid) {      
        System.out.println("This is an equilateral triangle");
      }
      else {
        System.out.println("This is an isosceles triangle");
      }
    }
  }

  public double perimeter() {
    // calculate the perimeter
    double perimeter = max + mid + min;
    return perimeter;
  }

  public double area() {
    // calculate the area
    double semi = (max + mid + min) / 2;
    double product = (semi - max) * (semi - mid) * (semi - min) * semi;
    double area = Math.sqrt(product);
    return area;
  }
}

Answer 1

you need to intialize your input

    input = new Scanner(System.in);