A good answer might be:

The instance variables are used to store the state of an object. They will hold values for as long as the object exists.

The formal parameters of a method can be "seen" only by the statements of their own method. This means that if a method tries to use a parameter of some other method, the compiler will find a syntax error.

Here is the CheckingAccount class again, this time with a new definition of the display() method

class CheckingAccount
{
  . . . .
  private int    balance;

  . . . .
  void  processDeposit( int amount )
  {
    balance = balance + amount ; 
  }

  // modified display method
  void display()
  {
    System.out.println( balance + "\t" + amount );
  }

}

QUESTION 4:

Is this display() method correct?