Why Error handling is not recommended?

Question

I know that we should not handle Error in java using try catch, but I tried it for learning and found that we can handle Error similarly Exception using try catch block. Even code after catch block is also getting execute. I generated a StackOverFlowError but still I can initialize local variable. Can any one please explain it?

import java.util.LinkedList;
import java.util.List;

public class ExceptionDemo {

    public static void main(String[] args) {
        try{
              method1();
        }
        catch(Error e){
            System.out.println(e.getStackTrace());

            System.out.println("Hello world");
            int a =10;
            System.out.println(a);          
            method();   
        }       
        System.out.println("Hello world2");
    }

    public static void method1(){
        method1();
    }   

    public static void method(){
        List l1 = new LinkedList();
        l1.add("A");        
        int[] aa = new int[10000];
        aa[0]=25;
        System.out.println(aa[0]);

        int b =10;
        int c = 20;     
        System.out.println( b +""+c);
    }
}

Output of this class is -

 [Ljava.lang.StackTraceElement;@1db9742

Hello world
10
25
1020
Hello world2

Welcome to Stack Overflow! Please take the [tour], have a look around, and read through the [help], in particular [*How do I ask a good question?*](/help/how-to-ask) — T.J. Crowder, Feb 09 '17 at 07:56
But still I can initialize object and local variables , how it is happening ? — Ashok Singh, Feb 09 '17 at 07:56
Possible duplicate of [When to catch java.lang.Error?](http://stackoverflow.com/questions/352780/when-to-catch-java-lang-error) — shmosel, Feb 09 '17 at 07:57
`should not handle` != `can not handle ` You can but you should not (in general) — AxelH, Feb 09 '17 at 07:58
@Bathsheba, could you provide a source ? I always heard that a program should rarely recover from an `Error`. There is exception to this rule but in general, `Error` should simply end the program (or be catch to stop properly the program). You seems to have an other view of this, I would be interested by this. — AxelH, Feb 09 '17 at 08:03
@Bathsheba You are missing the point--the OP is asking why we shouldn't catch `Error`s. — chrylis -cautiouslyoptimistic-, Feb 09 '17 at 08:05
@Bathsheba - The javadoc says: *"An Error is a subclass of Throwable that indicates serious problems **that a reasonable application should not try to catch.**"*. Is that clear enough for you? — Stephen C, Feb 09 '17 at 08:05
[trivial edit so I can retract my question downvote], and voted to reopen. — Bathsheba, Feb 09 '17 at 08:09
@Bathsheba Thanks! And I like your avatar cat; may my upvotes translate to badges and earn that cute cat some cuddling in my name! Cats rule! — GhostCat, Feb 09 '17 at 08:11

score 5 · Answer 1 · edited May 23 '17 at 11:54

5

I focus in my answer on that part of your question that is not related to the "why not catch Errors"; but your implicit idea that you "can't catch Errors". Because: that idea of yours is simply wrong!

You can catch all subclasses of Throwable. Just look at the words: everything that can be thrown can also be caught.

Error is a subclass of Throwable!

But you are correct about the fact that only instances of that other child-class called Exception of Throwable should be caught using try/catch. For "why not catch errors"; that is explained extensively over here!

edited May 23 '17 at 11:54

Community

1
1

answered Feb 09 '17 at 07:57

GhostCat

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The problem is that if an error has happened, you can't guarantee that the JVM is going to work correctly from that point. Sure, it will let you catch it and try to do some things (after all, it makes sense to log the error) but you should consider your program to be unstable at that point. – D M Feb 09 '17 at 08:10
1

That is what the last paragraph is pointing to in the end. And just for the record: it really depends: we have a distributed environment, and sometimes, when I put the wrong version of some java class on another system, that causes MethodNotFoundErrors on that systems. And we actually catch those (LinkageErrors methinks) because we know they can happen when we mess up; and catching them allows us to do the required cleanup when our operations fail. – GhostCat Feb 09 '17 at 08:13

Why Error handling is not recommended?

1 Answers1