What is the error in my exception and the throw and getMessage?

Question

I have code and i want to know where is the error, please can you help me: only one error on the throw line

public static void main(String[] args) {
    try {
        Scanner input = new Scanner (System.in);
        System.out.println("Enter the number ");
        int x1 = input.nextInt();
        int i;
        if (x1>=0&&x1<=100) {
            i= (int) Math.pow(x1,2);
            System.out.println("the squre of  "+ x1 + " is "+ i);
        }
        else 
            throw new MyException();   // what is the error here?
    } catch(MyException me) {
        System.out.println(me);
        String message = me.getMessage();
    }
}

public class MyException extends Exception {
 public String getMessage() {
        return " the number is out of ring";
    }
    }

}

Is this your actual code? Your throw/catch statement looks wrong. Can you clean up the post please! — Alvin Bunk, Oct 21 '14 at 23:58
What did the compiler say the error was? By the way, I do _not_ get an error on `throw new MyException()`. — ajb, Oct 22 '14 at 00:03
I've tried to clean up the post so others can understand it. Obviously there's a `}` where it doesn't belong after `MyException`. I do not know why you're getting an error on the `throw`, since I don't get one; you will need to tell us what the compiler says the error is. — ajb, Oct 22 '14 at 00:10
non-static variable this cannot be referenced from a static context — Ghada Ali Othman, Oct 22 '14 at 00:10
@Victor2748 sorry for stepping on your edit, I've tried to recreate it... — ajb, Oct 22 '14 at 00:21

score 0 · Accepted Answer · answered Oct 22 '14 at 00:01

0

First of all, your getMessage method is outside of you MyException class. Secondly, you are trying to call a method called getMessage(), which cannot be done in the main method, you have to call me.getMessage();

answered Oct 22 '14 at 00:01

Moddl

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thank you i edit it . put i still have an error on the throw line – Ghada Ali Othman Oct 22 '14 at 00:17

score 0 · Answer 2 · answered Oct 22 '14 at 00:18

0

It looks like you haven't quite posted your entire class, but based on the error message it looks like MyException occurs inside your class, something like:

public class TheClass {

    public static void main(String[] args) {
        ....
    }

    public class MyException extends Exception {
        ....
    }

}

This makes MyException an inner class. Every instance of MyException must therefore "belong" to an instance of TheClass. That's why you get the "non-static variable this" error message. When you say new MyException, you're inside the static main method, so it has no way of knowing what instance of TheClass the new MyException object will belong to.

I don't think you want this to be an inner class. Either move MyException outside of TheClass, or make it static:

public static class MyException extends Exception {

Making it static would make it a "nested" rather than an "inner" class, so that it doesn't belong to an instance of TheClass. You probably want to move it outside, though. I don't see a good reason for it to be in your other class.

answered Oct 22 '14 at 00:18

ajb

31,309
3
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i still have one error on the throw line – Ghada Ali Othman Oct 22 '14 at 00:26
What change did you make, and is it the same error or a different one? **Please do not just tell us on StackOverflow that the compiler is giving you an error, without telling us what it is. Don't hide information from us.** – ajb Oct 22 '14 at 00:31
non-static variable this cannot be referenced from a static context – Ghada Ali Othman Oct 22 '14 at 00:34
@GhadaAliOthman Did you make either of the changes I suggested in my answer? If so, which one? – ajb Oct 22 '14 at 00:34
on the throw line .. i edit my post – Ghada Ali Othman Oct 22 '14 at 00:35
public class MyException extends Exception { public String getMessage() { return " the number is out of ring"; } } – Ghada Ali Othman Oct 22 '14 at 00:35
@GhadaAliOthman I suggested either making `MyException` static or moving it outside your main class. Did you make either of those changes? – ajb Oct 22 '14 at 00:38

What is the error in my exception and the throw and getMessage?

2 Answers2