16. Method Overloading

Answer:
mystA sum: 15 mystB sum: 20
The instance variable in mystB did not change.
The trick: the parameter sum of the second method shadowed the instance varaible.

Method Overloading

Overloading is when two or more methods of a class have the same name but have different parameter lists. When a method is called, the correct method is picked by matching the actual parameters in the call to the formal parameter lists of the methods.

Review: another use of the term "overloading" is when an operator calls for different operations depending on its operands. For example + can mean integer addition, floating point addition, or string concatenation depending on its operands.

Say that two processDeposit() methods were needed:

• One for ordinary deposits, for which there is no service charge.
• One for other deposits, for which there is a service charge.

public class CheckingAccount
{
  . . . .
  private int balance;

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

  public void processDeposit( int amount, int serviceCharge )
  {
    balance = balance + amount - serviceCharge; 
  }

}

The above code implements these requirements. Here is an example main() method that uses both methods:

class CheckingAccountTester
{
  public static void main( String[] args )
  {
    CheckingAccount bobsAccount = new CheckingAccount( "999", "Bob", 100 );
    
    bobsAccount.processDeposit( 200 );       // statement A
    
    bobsAccount.processDeposit( 200, 25 );   // statement B
  }
}

Question 16:
Examine main().
Which method, processDeposit(int) or processDeposit(int, int) does each statement call?
statement A calls 
statement B calls