Try and catch printing error

Question

My program takes input from a user, first number, operation ( + - * / ^) then a second number. When I enter 5 / 0 it says ERROR!!! Cannot divide by 0 . That's what its supposed to do. However, When I type in 5 / 5 which is 1 I get my error message.

do {
    try {
        if (opperation == "/" && num2 == 0);
        throw new ArithmeticException();
    } catch (ArithmeticException ae) {
        System.out.println("ERROR !!! Cannot divide by 0");
    }
    System.out.println("Enter First Number");
    num1 = scan.nextInt();
    System.out.println("ENTER Opperation: ");
    opperation = scan.next();
    System.out.println("ENTER Second Number: ");
    num2 = scan.nextInt();
} while (num2 == 0);

This question appears to be off-topic because it is yet another semicolon after an if-statement — Simon Forsberg, Oct 25 '13 at 23:28
Also, on top of what tbodt and I have said, see http://stackoverflow.com/questions/513832/how-do-i-compare-strings-in-java — Dennis Meng, Oct 25 '13 at 23:32

score 2 · Accepted Answer · answered Oct 25 '13 at 23:28

You have a stray semicolon in your if-statement. It should be

if (opperation == "/" && num2 == 0)
    throw new ArithmeticException();

instead of

if (opperation == "/" && num2 == 0);
    throw new ArithmeticException();

What you have is basically the same thing as

if (opperation == "/" && num2 == 0) {

}
throw new ArithmeticException();

score 1 · Answer 2 · answered Oct 25 '13 at 23:28

You shouldn't have a semicolon after your if statement. This makes the body of the if statement into nothing. Change it to this:

if (opperation == "/" && num2 == 0)
    throw new ArithmeticException();

Your IDE seems to have caught this and reindented the code for you, in the wrong way.

By the way, that isn't how you use ArithmeticException. A line of code that divides by 0 will automatically throw an ArithmeticException, and you can catch it then. However, that is slower than not using ArithmeticException at all:

if (opperation == "/" && num2 == 0)
    System.out.println("ERROR !!! Cannot divide by 0");

Try and catch printing error

2 Answers2