Defining Classes I - Java - page 182

Display 4.5 Correspondence between Formal Parameters and Arguments

This is in the file
DateThirdTry.java .

public class DateThirdTry
{
private String month;
private int day;
private int year; //a four digit number.

public void setDate( int newMonth, int newDay, int newYear)
{
month = monthString(newMonth);
day = newDay;
year = newYear;
}
...

Only the value of year ,
namely 1882 , is plugged in
for the parameter newYear .

This is in the file
DateThirdTryDemo.java .
This is the file for a program that
uses the class DateThirdTry .

public class DateThirdTryDemo
{
public static void main(String[] args)
{
DateThirdTry date = new DateThirdTry( );
int year = 1882;
date.setDate(6, 17, year);
date.writeOutput( );
}
}

The arrows show which argument is
plugged in for which formal
parameter.

Parameters of a Primitive Type
Parameters are given in parentheses after the method name in the heading of a method
definition. A parameter of a primitive type, such as int , double , or char , is a local variable.
When the method is invoked, the parameter is initialized to the value of the corresponding
argument in the method invocation. This mechanism is known as the call-by-value parame-
ter mechanism. The argument in a method invocation can be a literal constant, such as 2 or
'A' ; a variable; or any expression that yields a value of the appropriate type. This is the only
kind of parameter that Java has for parameters of a primitive type. (Parameters of a class
type are discussed in Chapter 5.)