[SOLVED] COMP1213 Activity 11-Exception Handling 

Activity: Exception Handling

Goals:

By the end of this project you should be able to do the following:
Ø Handle exceptions that can occur in your program using a try-catch statement Ø Throw exceptions in your program

Directions:

Don’t forget to add your Javadoc comments for your classes, constructor, and methods in this activity.

For this assignment, you will be creating two classes: Division and DivisionDriver

Division: methods

• Division has two public static methods:
  o intDivide: takes two int parameters (a numerator and denominator), performs

  integer division, and returns the int result of dividing the numerator by the

  denominator.
  o decimalDivide: takes two int parameters (a numerator and denominator),

  performs floating point division (you’ll have to use casting), and returns the result of dividing the numerator by the denominator.

• Test your methods in the Interactions pane:

  DivisionDriver

• DivisionDriver contains a main method only. The program will get a numerator and denominator from the user and print the integer division and decimal division result.
• Create a dialog box that will get the numerator and denominator as a String (you’ll have to import the JOptionPane class in the javax.swing package):
• Convert each to an integer value using the static parseInt method in the Integer class:

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• Create a String object to hold the result of the division:
• Print the result in a dialog box:
• Test your method by running the driver program with numerator 19 and denominator 5:
• Now try entering an invalid number in the dialogs (five and ten):

  Your program should generate a run-time error in the form of a NumberFormatException exception:

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• The exception occurs when the parseInt method tries to convert the String “five” to an integer. The Java API listing for parseInt lists the exception that it might throw.
• Use a try-catch statement to catch the exception and tell the user what went wrong without creating a run-time error:

  Existing code

• Try entering invalid values five and ten once more for numerator and denominator once more. You should now get the following error:

  Exception Throwing

• Try the following in the interactions pane: Division.intDivide(10, 0)

  java.lang.ArithmeticException: / by zero

• Try to run your driver program with the numerator 10 and denominator 0:

—-jGRASP exec: java DivisionDriver

Exception in thread “main” java.lang.ArithmeticException: / by zero

at Division.intDivide(Division.java:7)
at DivisionDriver.main(DivisionDriver.java:12)

—-jGRASP wedge: exit code for process is 1. —-jGRASP: operation complete.

• The exception is generated in the intDivide method and not caught/handled, so it is propagated to main where it is also not caught/handled. Next we want to catch the exception in the intDivide method so that it will not be propagated to the main method.
• In your intDivide method, add code that will return 0 if an ArithmeticException occurs and the division result otherwise:

  Existing code

  Run DivisionDriver with inputs 10 and 0. The result should be 0 for integer division:

• Suppose that you do not want users to be able to divide by 0 in your decimalDivide method. Division.decimalDivide(10, 0)

  Infinity

  The IllegalArgumentException in the Java API can be thrown if a particular argument (parameter) to a method is not allowed: http://download.oracle.com/javase/6/docs/api/java/lang/IllegalArgumentException.html

• In your decimalDivide method, throw an IllegalArgumentException if the denominator is zero:

  if (denom == 0) {
  throw new IllegalArgumentException(“The denominator “

}

+ “cannot be zero.”);

Activity: Exception Handling Page 5 of 5

• Test your method again in interactions. You should now see the exception: Division.decimalDivide(10, 0)

  java.lang.IllegalArgumentException: The denominator cannot be zero.

• In your main method, add another catch statement to catch the exception that is thrown by the decimalDivide method. This time, print the exception text itself (stored by variable errorMessage):

  Existing code

• Now try dividing by 0 in your program. You will get the following error message instead of a run-time error:
• Run Checkstyle on each of your files and make any necessary corrections indicated by audit errors.
• Finally, submit your files to the grading system.