I don't know why my variable cannot be resolved to a variable

Question

I don't know why the code cannot run. The compiler only said the "p cannot be resolved to a variable" and "q cannot be resolved to a variable" on Line 45. I have search the solution on the internet, but still no have a good way to solve this.

import javax.swing.JOptionPane;

public class Rumus_GUI 
{
    public static void main(String[] args)
    {

       int a = Integer.parseInt(JOptionPane.showInputDialog("PLEASE ENTER THE VALUE OF A"));

       int b = Integer.parseInt(JOptionPane.showInputDialog("PLEASE ENTER THE VALUE OF B"));

       int c = Integer.parseInt(JOptionPane.showInputDialog("PLEASE ENTER THE VALUE OF C"));

        if (a==0)
            {
                JOptionPane.showMessageDialog(null,"THE VALUE OF A CANNOT BE 0.");
            }
        else
            {
                if (b<=-1)
                {
                    String p = "xx";
                }
                else if (b==0)
                {
                    String p = "";
                }
                else if (b>=1)
                {
                    String p = "xx+";
                }  
                else if (c<=-1)
                {
                    String q = "x";
                }
                else if (c==0)
                {
                    String q = "";
                }
                else 
                {
                    String q = "x+";
                }
            
                JOptionPane.showMessageDialog(null,"YOUR QUADRATIC EQUATION IS : "+a+p+b+q+c+"=0");

   
            }
    
    }

}