Homework 10

1. SafeIntArray class (5 points)

A student had a good idea and defined a new SafeIntArray class that would throw a descriptive ArrayIndexOutOfBoundsException whenever someone tried to read from a location that did not exist in the array. This new class gives some more information in the error messages generated by the getElementAt method. However, they forgot to apply the idea to the setElementAt method, which allows someone to write a value to particular location in the array.

• Modify the setElementAt method in the SafeIntArray class so that it will throw an ArrayIndexOutOfBoundsException when a specified index is less than 0 or greater than the last possible index in the array. (HINT: refer to the getElementAt method as a guide)

2. SafeIntArrayTest class (10 points)

The student also defined a test class SafeIntArrayTest to test the functionality of their new SafeIntArray class. Unfortunately, their test program crashes whenever an out of bounds index is entered by the user. Fix this problem in two ways (you should have two separate modified SafeIntArrayTest programs when you are done):

• Insert some try and catch statements to keep the program from crashing. If the user enters an index that is out of bounds, your modified program should catch the resulting exception, tell the user they went out of bounds, and allow them to continue entering values. A possible output might look something like the following:

        Please enter an index to read (-1 to quit): 12
  
          the element at index 12 is 35
  
        Please enter another index (-1 to quit): 34
  
          index 34 exceeds the maximum index [19]
  
        Please enter another index (-1 to quit): -2
  
          index -2 precedes the minimum index [0]
        

• Instead of using the try and catch statements, just test to make sure that the index [entered by the user] is not out of bounds before you call the getElementAt method. The user should again be able to continue entering values after a bad index (just like above). The only difference is you are checking for a bad value before you try and retrieve it, instead of just trying to retrieve the value at the specified index and catching the execption, as in the previous problem.