Methods
?customer example
Continuing with the Customer example:
suppose we need the program to be able to print each customer's account
balance on the screen (perhaps using System.out.println()
or Graphics.drawString()
). A sensible place to put the instructions for this is in a method called
`printBalance' (for example). We might define this method like this:
class
Customer
{
String
name;
String
address;
int
accountBalance;
int
creditLimit;
// printBalance
method
//
prints the customer's balance
public void printBalance ()
{
System.out.println
("Current balance for "
+ name
+ " is "
+ accountBalance
+ " pounds");
}
}
In a specific object of this class, assume
the customer's name is Fred Bloggs and the account balance is 2,000 pounds,
then executing this method would print:
Current
balance for Fred Bloggs is 2000 pounds
Look carefully at the start of the definition
of printBalance:
public
void printBalance ()
The keyword `public'
loosely means `can be called by methods outside
this class'. This concept is discussed in more later this unit.
The keyword `void'
means that this method has no return value ('output').
The empty parentheses (brackets) mean that the method has no arguments
('inputs').
It is often pointed the printBalance
does have a form of output: it produces an output
on the screen. This confusion is the reason why we tend to use the term
'return value' here rather that 'output'. When it is said that printBalance
has no return value, what is meant is that it would be meaningless to write
a line like:
x
= printBalance();
because nothing useful would be put into
the variable x in this case. In other words,
there is no output in the form of a reply returned to the message statement
that invoked the method.
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