Hi Friend,

Try the following code:

import javax.swing.*;
class  Customer{
        int bal;

        Customer(int bal) {
        this.bal = bal;
        }
        int deposit(int amt) {
                if (amt < 0) {
                        System.out.println("Invalid Amount");
                        return 1;
                }
                bal = bal + amt;
                return 0;
        }

        int withdraw(int amt) {
                if (bal < amt) {
                        System.out.println("Not sufficient balance.");
                        return 1;
                }
                if (amt < 0) {
                        System.out.println("Invalid Amount");
                        return 1;
                }
                bal = bal - amt;
                return 0;
        }
         void check() {
                JOptionPane.showMessageDialog(null,"Balance:" + Integer.toString(bal));
        }

    }
    public class Bank{
        public static void main(String[]args){
        Customer Cust=new Customer(1500);
        String st1=JOptionPane.showInputDialog(null,"Enter the amount to deposit:");
        int dep=Integer.parseInt(st1);
        int bal1=Cust.deposit(dep);
        Cust.check();
        String st2=JOptionPane.showInputDialog(null,"Enter the amount to withdraw:");
        int with=Integer.parseInt(st2);
        int bal2=Cust.withdraw(with);
        Cust.check();
        }
    }

Thanks