Help for write Bank application in Java

Hi.
I'm a student and I need write a programe bank application in java .
I must write a program that the customer could withdraw and deposit from his account.I wrote this program:
import java.util.Scanner;

public class BankAccount {

public static void main(String[] args) {
Scanner clapton=new Scanner(System.in);
int x;
float balance = 0;
boolean quit=false;
do {
System.out.println("1. Deposit money");
System.out.println("2. Withdraw money");
System.out.println("3. Check balance");
System.out.print(" 0 to quit: ");
System.out.println("enter your choice :");
x=clapton.nextInt();

if (x==1) {
float amount;
System.out.println(" enter your deposit money :");
amount=clapton.nextFloat();
balance + = amount;
}
else if (x==2) {
float amount;
System.out.println(" enter your Withdraw money :");
amount=clapton.nextFloat();
balance - = amount;
}
else if (x==3) {
System.out.println("your balance :" + balance );
}
else if (x==0) {
quit=true;
}
else {
System.out.println("wrong choice");
}

} while (!quit);
System.out.println("bye");
}
}

but I need to use several classes for this program. for exemple:
BankAccount which has an instance variable amount
and has methods:
withDraw which takes a parameter -> amountToWithDraw
deposit -> amountToAdd
checkBalance -> which takes no parameters, but which returns the value in the instance variable amount.
but i dont know how use of several classes.
you can help me?