Can't find the problem with this code pls help

Need help with basic java code

Hi guys. I need some help on this code. It compiles and I can get results when I run it on Netbeans but I always get RuntimeException.
I found out on Javadocs this is the superclass of those exceptions that can be thrown during the normal operation of the Java Virtual Machine. How can I get rid of it? Any thoughts? Thanks!

Code:

        // i++
        float Etplus, TrueEplus, TrueVplus, fplus1=0;
        //  Summation from i=1 to 10000
        for (int i=1;i<=10000;i++){
            fplus1 +=(float) 1/(Math.pow(i,4));
        }
        TrueVplus = (float) ((Math.pow(Math.PI, 4)) / 90);
        TrueEplus = (float) TrueVplus - fplus1;
        Etplus = (float)(TrueEplus/TrueVplus)*100;
   
        JOptionPane.showMessageDialog (null,"Ft(i++) = "+TrueVplus + "\n\nFa(i++) = " +fplus1 + "\n\nEt(i++) = ("+Etplus+ ")%","Results for i++ (Float)", JOptionPane.INFORMATION_MESSAGE);
       
        // i--
        float Etminus, TrueEminus, TrueVminus, fminus1=0;

        //  Summation from i=10000 to 1
        for (int j=10000;j>=1;j--){
            fminus1 += (double) 1/(Math.pow(j, 4));
        }

        TrueVminus = (double) (Math.pow((Math.PI), 4))/90;
        TrueEminus = (double) TrueVminus - fminus1;
        Etminus = (double) (TrueEminus/TrueVminus)*100;
        
        JOptionPane.showMessageDialog (null, "Ft(i--) = "
+TrueVminus + "\n\nFa(i--) = " +fminus1 + "\n\nEt(i--) = (" +Etminus+")%","Results for i--(Float)", JOptionPane.INFORMATION_MESSAGE);

 }

}