TestMyTriangle and MyTriangle

I am posting because one of my programs is not working properly. It is a program, well, two programs, that are supposed to check if a triangle is valid and then print the area. The problem is, it never says if it is invalid even when it is. I tried messing around with the loops and it will say if it is invalid but it will not print the area properly. Any help is greatly appreciated! Thanks in advanced!

/* Class:        CS1301
* Section:       8
* Term:          Fall 2015
* Name:          Matthew Woolridge
* Instructor:    Mr. Robert Thorsen
* Assignment:    Assignment 8
* Program:       3
* ProgramName:   MyTriangle
* Purpose:       Implements the methods in test my triangle
* Operation:     The information is statically instantiated in the code and
*                the data is output to the screen.
* Input(s):      The input is the sides
* Output(s):     The output will be if valid and if so the area
* Methodology:   The program will use loops and methods, as well as another jar to produce an output
*
*/



import java.util.Scanner;

public class MyTriangle 
{

   public static void main(String[] args) 
   {

   /******************************************************************************
   *                          Declarations Section                               *
   ******************************************************************************/
   /****************************CONSTANTS********************************/
      double side1;
      double side2; //Declares side
      double side3;
      String restart = "y"; //Restart string
      Scanner scan = new Scanner(System.in);  //Intializes the scanner
      TestMyTriangle valid = new TestMyTriangle();  //Creates a new triangle test from the other program

    /******************************************************************************
   *                             Inputs Section                                  *
   ******************************************************************************/

      while(restart.equals("y"))
      {
         System.out.print("Enter three edges of the triangle: ");  //Prompts the user for the input of the sides
         side1 = scan.nextDouble();
         side2 = scan.nextDouble();
         side3 = scan.nextDouble();
      /******************************************************************************
      *                             Processing Section                            *
      ******************************************************************************/


         if (!valid.isValid(side1,side2,side3)) {  //Prints if the input is invalid
            System.out.print("The input is invalid");
            System.exit(0);
         }

      /******************************************************************************
      *                              Outputs Section                                *
      ******************************************************************************/   
         System.out.print("The area of the triangle is  "  //Prints the area of the triangle if valid 
            + valid.area(side1,side2,side3) + "\n");

         System.out.println("Would you like to restart? Enter y or n: ");  //Asks to restart
         restart = scan.next();
      }
      System.out.print("The program has ended!");  
   } //Ends string
} //Ends program

/* Class:        CS1301
* Section:       8
* Term:          Fall 2015
* Name:          Matthew Woolridge
* Instructor:    Mr. Robert Thorsen
* Assignment:    Assignment 8
* Program:       3
* ProgramName:   TestMyTriangle
* Purpose:       Tests the triangles sides to see if they are valid or invalid
* Operation:     The information is statically instantiated in the code and
*                the data is output to the screen.
* Input(s):      The input is the sides, in the other program
* Output(s):     The output will be valid or invalid in the boolean
* Methodology:   The program uses booleans to see if the sides are valid and then it calculates the area and returns to MyTriangle
*
*/


public class TestMyTriangle extends MyTriangle
{

   public static boolean isValid(double side1, double side2, double side3) 
   {
      return !(side1>side2+side3||side2>side1+side3||side3>side1+side2);
   }

   public static double area(double side1, double side2, double side3)
   {
      double s;
      double area;
      s = (side1 + side2 + side3)/2;
      area = Math.sqrt(s*(s-side1)*(s-side2)*(s-side3));
      return area;
   }
}