public class BankAccount {

    public BankAccount () { this(0.0) ; } 
   
    public BankAccount( double initBal )
       { balance_=initBal; id_=newID(); }

    public double balance() { return balance_; }
    public int   id()       { return id_; }

    public void withdraw(double amt) { balance_ -=amt; }
    public void  deposit(double amt) { balance_ +=amt; }

    public String toString()    
       { return super.toString() + "(id:" + id_ + ", bal:" + balance_ + ")" ; }

    // Instance variables
    private double balance_;
    private int id_;

    // Class variable and class method
    public static int nextID_=100;
    private static int newID() { return nextID_++; }

    // Another "special" class method
    public static void main(String args[]) {

    BankAccount a=new BankAccount(15.25);
    BankAccount b=new BankAccount();

    System.out.println("a=" + a.toString() );
    System.out.println("b=" + b.toString() );

    a.withdraw(5.50);
    b.deposit(125.99);

    System.out.println("a=" + a);
    System.out.println("b=" + b);

    System.exit(0);     
    } // no semi-colon
}

Detailed Description:

"Once we've got our two objects created, we want to print them out. And so, there is a construct in the system, to go to the System class, get the out variable, which is a PrintStream and print information into the stream. So notice the construct. We have System.out.println(...). System is a class, out is a class variable that's a PrintStream. And println is a method on that class that writes out a String to the console. The string is the arguments passed to println, "a=" followed by a plus sign (+) that does concatenation to a.toString(). The result is it's going to say "a=" and whatever information BankAccount's toString does. Its job is to print out what the super.toString() creates and then print out the id and the balance. The next one does the same except it works with BankAccount 'b'."