Lecture 5 Objectives

Lecture 5 Objectives [Oct 31]prev next

OPENING LINE: There was no possibility of taking a walk that day [Jane Eyre, Charlotte Bronte]

At the end of today's class you should

HAVE READ:

pp. [338-362]

KNOW:

the concept of an array
how to define an array of a specific type
how an array has index values [0] ... [n-1] where n is the number of elements in the array
the use of new to instantiate an array
how two variables p and q can point to the exact same array, such that changing p[2] causes q[2] to also change
the concept of null.

BE ABLE TO:

instantiate an array ar of int with 5 elements and set ar[0] to 1, ar[1] to 2, ar[2] to 3, ar[3] to 4, and ar[4] to 5.

DAILY QUESTION:

What happens when you run the following program: (a) Describe the output that appears; and (b) why an Exception occurs.

public class Sample {
public static void main(String[] args) {
    String []values = new String[4];

    int idx = 0;
    while (idx < 5) {
      System.out.println (values[idx]);

      idx++; // ADVANCE
    }

    System.out.println ("DONE");
}
}

Sample Exam Question:

Write a program that instantiates an array of 3 int values, populates the array with the numbers 2, 4, and 7. Then output the numbers in reverse order by reading the values from the array using a while loop.

Go through all the steps in the design recipe in the development of your program.