//MAIN CLASS   import javax.swing.JOptionPane; public class exercise3_1 {   public static void main (String[]args){   // define a value for the each variables which are a,b,c   String aString=JOptionPane.showInputDialog("enter a number for a"); double a=Double.parseDouble(aString);   String bString=JOptionPane.showInputDialog("enter a number for b"); double b=Double.parseDouble(bString);   String cString=JOptionPane.showInputDialog("enter a number for c"); double c=Double.parseDouble(cString);   //compute the discriminant which is going to be necessery to compute the roots of the equation   double discriminant=(Math.pow(b,2.0)-4*a*c); String discriminantString=JOptionPane.showInputDialog("the discriminant is:"+discriminant); //the discriminant must be positive otherwise,the roots are undefineable. if (discriminant>=0){   double root1= (-b+Math.pow(discriminant,0.5))/(2*a); double root2= (-b-Math.pow(discriminant,0.5))/(2*a);   String output="the roots of the equation is:"+"\nroot1="+root1+"\nand root2="+root2; JOptionPane.showMessageDialog(null, output);   }   else{ JOptionPane.showMessageDialog(null, "WRONG NUMBERS!! VALUE OF THE DISCRIMINANT MUST BE POSITIVE!!"); }     JOptionPane.showMessageDialog(null,"MUSTAFA OGUZ DONMEZ   150713042");           } }