Chapter 12, Problem 12.1PE

Program Plan Intro

Program to throw the NumberFormatException exception

Program plan:

• Import the required packages into the program.
  • Create a class Exercise12_01 to throw the NumberFormatException exception.
  • In the main() method,
    • Declare the required variables.
    • Check whether the length of argument is not equal to 3. If yes, display error message.
    • In try block, assign the first argument value to variable.
    • In catch block, catch the exception if error occurs.
    • In try block, assign the third argument value to variable.
    • In catch block, catch the exception if error occurs.
    • Match the argument 1 with character 0 using switch case.
      • If case "+" matches, then add the two numbers and stores the result.
      • If case "-" matches, then subtract the two numbers and stores the result.
      • If case "." matches, then multiply the two numbers and stores the result.
      • If case "/" matches, then divide the two numbers and stores the result.
    • Display the result.

Program Description Answer

The below program demonstrates how to operate mathematical operations and throw a NumberFormatException exception if error occurs.

Explanation of Solution

Program:

Filename: Exercise12_01.java

//Class definition

public class Exercise12_01

{

//Main method

public static void main(String[] args)

{

//Declare and initialize variables

int num1, num2, result = 0;

/*Check whether the length of argument is not equal to 3. */

if (args.length != 3) {

//Display error message

System.out.println("please use java Exercise12_01 operand1 operator operand2");

//Exit the program

System.exit(1);

}

//In try block

try {

//Assign the argument 0 as "num1"

num1 = Integer.parseInt(args[0]);

}

//In catch block

catch (NumberFormatException ex) {

//Display the exception

System.out.println("Wrong Input: " + args[0]);

return;

}

//In try block

try {

//Assign the argument 2 as "num2"

num2 = Integer.parseInt(args[2]);

}

//In catch block

catch (Exception ex) {

//Display the exception

System.out.println("Wrong Input: " + args[2]);

return;

}

//Match the argument 1 with character 0

switch (args[1].charAt(0)) {

//If case "+" matches

case '+':

/*Add the num1 and num2 and stores the result */

result = num1 + num2;

//Break the program

break;

//If case "-" matches

case '-':

/*Subtract the num2 from num1 and stores the result. *

result = num1 - num2;

;

//Break the program

break;

//If case "." matches

case '.':

/*Multiply the num1 with num2 and stores the result */

result = num1 * num2;

;

//Break the program

break;

//If case "/" matches

case '/':

/*Divide the num1 by num2 and stores the result */

result = num1 / num2;

;

}

//Display the calculated result

System.out.println(args[0] + " " + args[1] + " " + args[2] + " = " + result);

}

}

Sample Output

Command to run the program:

java Exercise12_01 4 + 5

4 + 5 = 9

Additional Output:

java Exercise12_01 4 - 5

4 – 5 = -1

java Exercise12_01 4x - 5

Wrong Input: 4x