CODEWITHSUNDEEP
javaexceptionstack-overflow
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Reputation: 10220

Program throws Stack Overflow Error

The following program compiles correctly. What is causing the Stack Overflow Error? How is the exception pushed on to the stack? 

public class Reluctant {

    private Reluctant internalInstance = new Reluctant();

    public Reluctant() throws Exception {
        throw new Exception("I’m not coming out");
    }

    public static void main(String[] args) {
        try {
            Reluctant b = new Reluctant();
            System.out.println("Surprise!");
        } catch (Exception ex) {
            System.out.println("I told you so");
        }
    }
}

Upvotes: 2

Views: 148

Answers (3)

Tagir Valeev
Tagir Valeev

Reputation: 100249

You have a field initialization code which is automatically added to the constructor body by javac compiler. Effectively your constructor looks like this:

private Reluctant internalInstance;

public Reluctant() throws Exception {
    internalInstance = new Reluctant();
    throw new Exception("I’m not coming out");
}

So it calls itself recursively.

Upvotes: 4

ssantos
ssantos

Reputation: 16536

You have an infinite loop. Every instance of Reluctant class instantiates another Reluctant object on internalInstance declaration. So, when you instantiate the first Reluctant object on your main method, the program creates one instance after another, over and over again, till the stack overflows.

Replace this line.-

private Reluctant internalInstance = new Reluctant();

for 

private Reluctant internalInstance;

Upvotes: 2

elixenide
elixenide

Reputation: 44841

This line in your main method results in infinite recursion:

Reluctant b = new Reluctant();

Every time you try to create an instance of Reluctant, the first thing you do is create another instance, which creates another instance, which creates another instance, which... You get the idea.

Voila, stack overflow!

Upvotes: 4

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