Question

CIT 149 Java 1 programming question

Use DrJava to compile the following try-catch program

? The Assignment

? Specifications

General

• Structure your file name and class name on the following pattern:
  • The first three letters of your last name (begin with upper case.).
  • Then the first two letters of your first name (begin with upper case.).
  • Follow this with the name of the program: TryCatch.
  • For a student called ’John Doe,’ the class name and file name would be: DoeJoTryCatch
• Use good comments in the body of the program.
• Think about the problem and decide what type each of the input numbers should be. Also, think about the calculations and decide what type the variables should be that will hold the results of the calculations.
• Use camel casing for variable names, and use descriptive variable names. Do not use general variable names like "tax" or "total."

Make sure you have the following comments at the beginning of your program:

/*
 * Program Name:   The program name.
 * Author:         Your first and last name.
 * Date Written:   The current date.
 * The class name: CIT 149 Java 1
 * Description:    Meaningful description of the purpose of the program.
 */

• Take a look at the method below.
  This method will cause the program to crash.

• Example 1: A method that tries to perform an impossible task

public static void watchThis()
{
    int theFirstNumber = 5;
    int theSecondNumber = 0;
    int theAnswer = theFirstNumber / theSecondNumber;  // <1>
    return;
}

<1> This is where the program crashes. I hope that at this point you understand why.

• Here is another example of a method that asks for an int and displays the number entered.
  A good way to handle a situation like this is to have a method (think one task) that will return an int from the user, but will continue to ask for input until an int is received. This would prevent a type mismatch and cause the program to end.
  You could use this method any time you needed an int from the user. You might also create a method for doubles as well.
  You would not put the prompting in the method because the prompting would be different in each program.

Example 2: A method that will return an int.

public static int getInt()
{
    while(true)    //  <1>
    {
        try
        {
            return keyboard.nextInt();   // <2>
        }
        catch(InputMismatchException e)
        {
            keyboard.next();             // <3>
            System.out.print("That is not and integer. Please try again: ");
        }
    }
}

<1> Using while(true) will create an infinite loop. The return statement will take it out of the loop.
<2> This is a normal int input statement. You could set this to a variable as well, and then return it. As it is, you need to have a variable set to store it in when it is returned.
<3> The next() statement discards the previous input. That is its only purpose.

? The Problem

? You will have a good bit of leeway in completing this problem.
You may create any problem you like, as long as it meets the specifics below. It can be written to display the results in the terminal, or it can be written in GUI style.

• The program must use OOP style and have more than one class containing methods.
• The program must at some point ask the user for the input of numbers.
• There must be methods to handle the input of the numbers to insure that type mismatches should not crash the program.
• The program must do at least one calculation. If it is possible to have a division by zero, there should be a try-catch to catch it and prevent the program from crashing.
• There must be at least one try-catch statement in your program.

Answer 1

==========================

JAVA Program

==========================

/////DoeJoTryCatch.JAVA//////////////////

import java.util.InputMismatchException;

import java.util.Scanner;

/**

* Program Name: CIT 149 Java1 Programming

* Author: John Doe

* Date Written: 11/27/2019

* The class Name: DoeJoTryCatch

* Description: The program will take 2 numbers from

* user and try to divide number1 by number 2 and display the result

*

*/

public class DoeJoTryCatch {

//private static field keyBoard, which is a scanner to read input from keyboard

private static Scanner keyBoard = new Scanner(System.in);

public static void main(String[] args){

System.out.println("Enter number1: ");

int num1 = getInt();//call getInt() to read a valid int from user

System.out.println("Enter number2: ");

int num2 = getInt();//call getInt() to read a valid int from user

System.out.println("Doing division of "+num1+" by "+num2+"...");

division(num1,num2);//call division() method to divide num1 by num2

}

/**

* Get a valid int from user.

* Take input from user until a valid integer value is not provided

* @return

*/

public static int getInt(){

while(true){//start infinite while loop

try{

return keyBoard.nextInt();//return int as read from scanner

}catch(InputMismatchException ime){//exception will be caught if proper input not given

keyBoard.next();//clear the previous input

System.out.println("This is not an integer. Please try again.");

}

}

}

/**

* Divide number1 by number2 and return integer result

* print error message if there is division by zero issue.

* @param number1

* @param number2

*/

public static void division(int number1, int number2){

int result = 0;

try{

result = number1/number2;

System.out.println("Result of division is = "+result);

}catch(ArithmeticException ae){//if division by 0, exception will be caught

System.out.println("Result undefined : division by zero error.");

}

}

}

=========================

OUTPUT

=========================

RUN1

-----

Enter number1:

25

Enter number2:

a

This is not an integer. Please try again.

5d

This is not an integer. Please try again.

5

Doing division of 25 by 5...

Result of division is = 5

RUN2

-----

Enter number1:

xyz

This is not an integer. Please try again.

68

Enter number2:

ys

This is not an integer. Please try again.

#

This is not an integer. Please try again.

4

Doing division of 68 by 4...

Result of division is = 17

RUN3

-----

Enter number1:

50

Enter number2:

0

Doing division of 50 by 0...

Result undefined : division by zero error.