please explain, please help

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I thought I executed previous suggestions correctly but apparently I did not understand. Could somebody please explain to me what is wrong? Where I went wrong? How to fix it?

1. There are three exceptions that successively inherit Exception.
2. The Exception1 class extends Exception
3. The Exception2 class extends Exception1
4. The Exception3 class extends Exception2
5. There is a method with the following signature:
public static void method1() throws Exception1, Exception2, Exception3
6. Write a catch block that will catch all three exceptions: Exception1, Exception2, and Exception3

Requirements:

The main method must call method1.
The main method must catch the Exception1 exception.
The main method must catch the Exception2 exception.
The main method must catch the Exception3 exception.
Don't change the method1 method.

package com.codegym.task.task09.task0914; /* Catching a group of exceptions */ public class Solution { public static void main(String[] args) throws Exception { //write your code here try { method1 ( ); } //write your code here catch (Exception3 e) { printStackTrace(); } catch (Exception2 e) { printStackTrace(); } catch (Exception1 e) { printStackTrace(); } } public static void method1() throws Exception1, Exception2, Exception3 { int i = (int) (Math.random() * 3); if (i == 0) throw new Exception1(); if (i == 1) throw new Exception2(); if (i == 2) throw new Exception3(); } class Exception1 extends Exception { } class Exception2 extends Exception1 { } class Exception3 extends Exception2 { } } /* class Solution { public static void main( String args[] ) { method1(); } public status void method1() { try { int num1 = 5/0; } catch (Throwable e) { e.printStackTrace(); } } } */

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David Haines

Level 13 , La Crosse, United States

29 September 2020, 00:14

Nouser - YOU ROCK!!! THANK YOU!!! Is there any way I could have found this tidbit? -- The printStackTrace was accidental leftovers from a previous effort. Good catch - thanks for pointing that out! -- I would have NEVER thought of moving the Exception classes outside of the Solution class. I saw nothing in any previous lessons to indicate that was a possible, viable, realistic option. Nor did I see anything like that in any of the items I came across using GOOGLE

Nouser

Level 36 , Germany

29 September 2020, 09:35

Syntactically it wasn't correct to have a class inside another. Possible would be to have a static class inside a class. So the other way to solve that would be to make the Exception1-3 classes static (make them an inner class). Afaik it is not possible to have 2 classes inside of one file but it works with classes extending exceptions that are package-private. Probably convenience reasons. But as said, at this time you can't know that. Even later you can't say it's easy stuff.. at least for me it is not ;)

Nouser

Level 36 , Germany

28 September 2020, 06:51

two problmes I see.. 1. the printStackTrace is called on an object, here e is obvious. However to test your code it's better to eg. just output 1 - 3. Tha tasks istself asks not for an output 2. Make the Exception1-3 classes not inner classes (move them outside the Solution class). You learn later why. The rest looks good. The point of the task is coded (catching Exception 3 before 2 before 1) so it should validate ;)

The Chief

Level 18 , United States

6 April 2021, 22:01

For this task, why is the catch block supposed to look like this?

catch (Exception exception) {
            System.out.println(exception);
        }

Shouldn't the catch be " catch(Exception e)"? Also, can the catch block be empty? Is the system.out.println really needed?

Nouser

Level 36 , Germany

7 April 2021, 07:40

e is just an identifier. You could name it whatever you like. But often you have nested or casceded catch blocks and then it may be useful to give the identifiers some more speaking names like ioe or IOException (or whatever you like). And usually you do not use the toString method on a throwable. Better to use printStackTrace as this will not just output the exceptions type and description but the entire stacktrace. But that's still not what you could call exception handling. That's just outputting the problem on the display (or the standard error stream). We do that here all the time but in real world programs you should use the catch block to fix the problem. If you want to load data and then just output IOExcetion (or nothing at all, as you asked, that's of course possible as well, but then it again is good practise to indicate that with naming the identifier 'ignored' or adding a comment), then that's not really satisfying for him. The program would continue either with corrupted data or no data at all. Instead you could tell the user that there may be a problem and then offer to try again or load the data from another file.