Java - JOptionPane.showInputDialog errors

Hello all I am experiencing issues with my JOptionPane.showInputDialog input field. The issue i am experiencing that is when the cancel button is selected or the OK button is selected with empty or with categorical i am greeted with an error. Any suggestions. My first attempt at fixing this i changed the c int into an interger therefore i could use an if statement along with null such as

Integer cInterger = new Integer(c);
  if (cInterger.equals(null)){
      return;}

Along with

cInterger == null
cInterger !=null

But to no avail

int a = 0;  //
int b = 0; //
int c = 0; //
    if (selected) {
        if (command.equals("amount")) { 
            Scanner readFile = null;
                try {
                    readFile = new Scanner(new FileReader("BANK.txt"));
                    } catch (FileNotFoundException e) {
                    // TODO Auto-generated catch block
                        e.printStackTrace();
                    } 
                    String account = "";
                    account = readFile.nextLine(); 
                    String amount = JOptionPane.showInputDialog(frame,"Enter an amount"); //assign user input to string amount
                    a= Integer.parseInt(account); //conversion of scanned string to int for easy subtraction                
                    b= Integer.parseInt(amount); 
                    c = a-b; 

                        try {  
                                if( c == 0){
                                    JOptionPane.showMessageDialog(null,"Granted.","Granted",JOptionPane.WARNING_MESSAGE);}
                                else if (c > 0){
                                    JOptionPane.showMessageDialog(null,"Granted.","Granted",JOptionPane.INFORMATION_MESSAGE); }
                                else{
                                    JOptionPane.showMessageDialog(null,"Denied.","Denied",JOptionPane.ERROR_MESSAGE);}