CodeGym/Help with Java Tasks/How to do I complete this task

Level 17

Savannah

04.12.2018
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11comments

How to do I complete this task

Question about the task

Static modifiers and exceptions

Java Core, Level 5, Lesson 9

Resolved

I threw the Exception, and got the message. How do I complete the task?

In a static block, throw an Exception
This will stop the class from loading, and you will see the following error message instead of the value of the variable B

Exception in thread "main" java.lang.ExceptionInInitializerError at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:186) at com.intellij.rt.execution.application.AppMain.main(AppMain.java:113) Caused by: java.lang.RuntimeException: at com.codegym.task.task15.task1517.Solution.(Solution.java:22)

Hint: Use Google to find the cause if you see the following:
java: initializer must be able to complete normally java: unreachable statement

Requirements:

An exception (Exception) must occur in a static block in the Solution class.
The program should not display anything (except an automatic message about the exception that occurs).
The program must not read data from the keyboard.
The Solution class must be public.

package com.codegym.task.task15.task1517; /* Static modifiers and exceptions */ public class Solution { public static int A = 0; static { throw new Exception(); } public static int B = 5; public static void main(String[] args) { System.out.println(B); } }

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Radosław Dziura

Level 16

28 May 2020, 09:27

And what's that supposed to teach us?

Level 20 , Toronto, Canada

30 December 2019, 19:20

public class Solution { public static int A = 0; static { if(true) throw new RuntimeException(); } public static int B = 5; public static void main(String[] args) { System.out.println(B); } }

+10

jim smith

Level 22 , Cedar Park, United States

29 January 2019, 17:21

embed in the if (true) clause and also only throw an unchecked exception type

Oleg Vanyushkin

Level 18 , St.-Petersburg, Russia

23 May 2019, 10:28

Thankies)

Jyothi

Level 20 , United States

23 December 2018, 21:42

solution

As recommended in the conditions I googled the error. so I added if (true) based on the google finding and verify passed. if (true) throw new NullPointerException(); Description FULL PRODUCT VERSION : java version 1.7.0-ea, build b76 ADDITIONAL OS VERSION INFORMATION : XP ver 5.1.2600 A DESCRIPTION OF THE PROBLEM : javac in java 1.6 as well as 1.7 b 76 allows the compilation of following: public class A { { if (true) throw new NullPointerException(); } A() { } } while for the following case without the if(true), it gives error: initializer must be able to complete normally public class A { { throw new NullPointerException(); } A() { } } This is ambiguous behaviour when we know that an intializer has to complete normally in all cases. The first case reported above hence is wrongly compiled. STEPS TO FOLLOW TO REPRODUCE THE PROBLEM : Use the example class A given above to compile. EXPECTED VERSUS ACTUAL BEHAVIOR : EXPECTED - Error : initializer must be able to complete normally ACTUAL - no error REPRODUCIBILITY : This bug can be reproduced always. ---------- BEGIN SOURCE ---------- public class A { { if (true) throw new NullPointerException(); } A() { } } ---------- END SOURCE ----------

+15

Benjamin Winchester

Level 17 , Savannah, United States

2 January 2019, 04:43

Thanks, that was it. Do you know the utility of this knowledge?

Michael Martin

Level 19 , Arlington, United States

7 December 2018, 01:58

Did you ever get this working?

Benjamin Winchester

Level 17 , Savannah, United States

7 December 2018, 03:19

No, The number of tasks I have backing up where I'm pretty certain I have met the conditions is getting pretty high. Maybe I need to shift over to Helsinki MOOC

Hashirama

Level 26 , Port-Harcourt, Nigeria

8 February 2019, 01:19

What's Helsinki MOOC ???

Hashirama

Level 26 , Port-Harcourt, Nigeria

8 February 2019, 01:24

Did you ever get this working? Yes it worked!!! This is my finding: first we can only throw a runtime exception in that Initializer block and second it must be in an if block --- reason being that an if block expression may or may not run. For instance, if we do this if (true) throw new ArithmeticException(); //Do this and verify. It will pass the verification test. This will compile. And the exception will be caught at runtime But if we do this: if (false) throw new ArithmeticException(); It will also compile, but no exception will be caught, and the program will run normally. The compiler has no idea what we have passed in the if (condition) But it knows that an if block may or may not execute base on condition.

Aditya Sinha

Level 17 , Bangalore, India

17 February 2019, 02:37

http://moocfi.github.io/courses/2013/programming-part-1/