JAVA Program to represent Bank System using inheritance function ,constructor and user input

import java.io.*;
/*Base class Account*/
class Account
{
 double accBal;
 Account()
 {
 }
 Account(double d)
 {
  accBal=d;
  if(accBal<1000)
  {
   System.out.println("Invlaid amount. Amount should be > or = 1000");
   accBal=1000;
  }
 }
 
 void credit(double amt)
 {
  accBal=accBal+amt;
 }
 
 void debit(double amt)
 {
  if(amt>accBal)
   System.out.println("Debit amount exceeded account balance");
  else
   accBal=accBal-amt;
 }
 
 double getBalance()
 {
  return(accBal);
 }
}
//Derived class SavingsAccount
class SavingsAccount extends Account
{
 double rate;
 SavingsAccount(double r,double amt)
 {
  super(amt); 
  rate=r;
 }

 public void calculateInterest()
 {
  accBal=accBal*rate;
 }
}
class CheckingAccount extends Account
{
 double fee;
 CheckingAccount(double f,double amt)
 {
  super(amt);
  fee=f;
 }
 void credit(double amt)
 {
  accBal=accBal+amt-fee;
 }
 void debit(double amt)
 {
  if(amt>accBal)
   System.out.println("Debit amount exceeded account balance");
  else
   accBal=accBal-amt-fee;
 }

 
}
class Bank
{
 public static void main(String args[])
 {
  int a,b;
  DataInputStream d= new DataInputStream(System.in);
  double amount,rate =5,fee=100;
 
  try
  {
  System.out.println("Press 1. SavingAccounts 2. Checking Accounts");
  a=Integer.parseInt(d.readLine());
  switch(a)
  {
  case 1:
  System.out.println("Enter amount to open account");
  amount=Double.valueOf(d.readLine());
  SavingsAccount sa=new SavingsAccount(rate,amount); 
  
  System.out.println("Thank you for opening account your Initial Balanceis :"+sa.getBalance());
  do
  {
  System.out.println("Enter choice:\n1.Withdraw\n2.Deposit\n3.CheckBalance\n 4.Exit");
  a=Integer.parseInt(d.readLine()); 
  switch(a)
  {
   case 1:
      System.out.println("Enter amount to withdraw");
      amount=Double.valueOf(d.readLine());
      sa.debit(amount);
      sa.calculateInterest();
      System.out.println("Balance is :"+sa.getBalance());
      break;
   case 2:
      System.out.println("Enter amount to deposit");
      amount=Double.valueOf(d.readLine());
      sa.credit(amount);
      sa.calculateInterest();
      System.out.println("Balance is :"+sa.getBalance());
      break;
   case 3:
      System.out.println("Your balance is"+sa.getBalance());
      break;
  }
  }
  while(a!=4);
  break;
  case 2:
  System.out.println("Enter amount to open account");
  amount=Double.valueOf(d.readLine());
  CheckingAccount ca=new CheckingAccount(fee,amount); 
  
  System.out.println("Thank you for opening account your Initial Balanceis :"+ca.getBalance());
  do
  {
  System.out.println("Enter choice:\n1.Withdraw\n2.Deposit\n3.CheckBalance\n 4.Exit");
  a=Integer.parseInt(d.readLine()); 
  switch(a)
  {
   case 1:
      System.out.println("Enter amount to withdraw");
      amount=Double.valueOf(d.readLine());
      ca.debit(amount);
      System.out.println("Balance is :"+ca.getBalance());
      break;
   case 2:
      System.out.println("Enter amount to deposit");
      amount=Double.valueOf(d.readLine());
      ca.credit(amount);
      System.out.println("Balance is :"+ca.getBalance());
      break;
   case 3:
      System.out.println("Your balance is"+ca.getBalance());
      break;
  }
  }
  while(a!=4);
  break;
  }
  }
  catch(Exception e)
  {}
 }
}