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recursion - Java : recursive constructor call and stackoverflow error

Please help to understand why does the following code

public class HeapQn1 {

    /**
     * @param args
     */
    public HeapQn1() {
        new HeapQn1();
    }

    static HeapQn1 n = new HeapQn1();

    public static void main(String[] args) {

    }

}

results in

java.lang.StackOverflowError
    at com.rg.test.interview.HeapQn1.<init>(HeapQn1.java:8)
    at com.rg.test.interview.HeapQn1.<init>(HeapQn1.java:9)
    ...

As per my understanding the memory allocation for an object happens in the heap memory and I was expecting an OutOfMemoryError as at some point the heap memory will be full because of repetitive object creation.

On research , I came across that a java constructor is considered a method and that explained the StackOverflowError , until I read the following thread.

When does the Constructor gets called in java?

which says

3. The object is fully constructed/created when the constructor returns.

From what I could gather , the constructor is a method and since the heap memory is much larger than stack memory , the recursive constructor call resulted in StackOverflowError . Is this correct ?

Since no object in the give code will get completely created , will stack frame allocation for constructor actually happen ?

--edit-- For the duplicates pointed out , I do understand what StackoverflowError is . I have mentioned in the question "On research , I came across that a java constructor is considered a method and that explained the StackOverflowError". My question is to understand if a constructor gets a stack frame allocated just like other methods as the object creation is not complete until the constructor returns. Hope this clarifies.

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1 Answer

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Whenever the constructor is called, its return address is pushed onto the stack. As the stack is finite and smaller than the heap memory, you are getting error like StackOverflowError rather than OutOfMemoryError.

The constructor is a method and since the heap memory is much larger than the stack memory, the recursive constructor call resulted in StackOverflowError. Is this correct ?

Yeah, your wild guess is completely correct. Cheers!


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