SOLVED COMP 1210 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: Division.intDivide(10, 3) 3 Division.decimalDivide(10, 3) 3.3333333333333335 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: Activity: Exception Handling Page 2 of 5 Page 2 of 5 • 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: ----jGRASP exec: java DivisionDriver Exception in thread "main" java.lang.NumberFormatException: For input string: "five" at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65) at java.lang.Integer.parseInt(Integer.java:580) at java.lang.Integer.parseInt(Integer.java:615) at DivisionDriver.main(DivisionDriver.java:9) ----jGRASP wedge: exit code for process is 1. ----jGRASP: operation complete. Activity: Exception Handling Page 3 of 5 Page 3 of 5 • 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: • 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) Existing code Activity: Exception Handling Page 4 of 5 Page 4 of 5 ----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: 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."); } Existing code Activity: Exception Handling Page 5 of 5 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): • 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. Existing code