Arrays

Goals

• Learn about Java arrays. An array is a data structure that can contain many items with the same data type.
• Practice coding common array-processing patterns (sum, min, max).
• Learn how to create a method that takes an array as an argument.
• Learn how to write a method that returns an array.
• Be aware of the fact that when an array is passed to a method, a reference is passed, which means that the method can change the array.

Setting up and accessing a fixed-length array (File: Five.java)

Download the file Five.java which contains "skeleton code." This is a valid Java program, but it doesn't yet do what we want it to.

Complete Five.java by doing the following:

1. Make the existing constructor work
2. Add a new constructor that accepts five integer arguments and places those arguments in the data array
3. Make the fillArray, sumArray and report methods work as described in the comments above them.
4. Add a getData method that takes no arguments and returns the instance variable that is an array of five integers. Why might it be a bad idea to have such a method?

> Five test = new Five();  
> test.sumArray()  0  
> test.report() 
 0 
 0  
 0  
 0  
 0  
 sum: 0  
> test.fillArray(0);  
> test.sumArray()  
100  
> test.report() 
 0  
10 
20  
30  
40  
sum: 100