Exploring Variable Length Parameter Lists
The file Parameters.java contains a program to test the variable length method average from Section 7.5 of the text. Note
that average must be a static method since it is called from the static method main.
1. Compile and run the program. You must use the -source 1.5 option in your compile command.
2. Add a call to find the average of a single integer, say 13. Print the result of the call.
3. Add a call with an empty parameter list and print the result. Is the behavior what you expected?
4. Add an interactive part to the program. Ask the user to enter a sequence of at most 20 nonnegative integers. Your
program should have a loop that reads the integers into an array and stops when a negative is entered (the negative
number should not be stored). Invoke the average method to find the average of the integers in the array (send the
array as the parameter). Does this work?
5. Add a method minimum that takes a variable number of integer parameters and returns the minimum of the
parameters. Invoke your method on each of the parameter lists used for the average function.
//*******************************************************
// Parameters.java
//
// Illustrates the concept of a variable parameter list.
//*******************************************************
import java.util.Scanner;
public class Parameters
{
//-----------------------------------------------
// Calls the average and minimum methods with
// different numbers of parameters.
//-----------------------------------------------
public static void main(String[] args)
{
double mean1, mean2;
mean1 = average(42, 69, 37);
mean2 = average(35, 43, 93, 23, 40, 21, 75);
System.out.println ("mean1 = " + mean1);
System.out.println ("mean2 = " + mean2);
}
//----------------------------------------------
// Returns the average of its parameters.
//----------------------------------------------
public static double average (int ... list)
{
double result = 0.0;
if (list.length != 0)
{
int sum = 0;
for (int num: list)
sum += num;
result = (double)sum / list.length;
}
return result;
}
}