为什么我要面对这个以及什么是工作流程

Question

Could anyone please help in understanding the StackOverFlowError at runtime in below code. I am not able to understand workflow. One of the interview Question:)

public class Interview {

    Interview i1 = new Interview();
    Interview(){
        System.out.println("Hello");

    }

    public static void main(String[] args){

        Interview i = new Interview();

    }

}

Answer 1

Your constructor is initializing itself. This is what your constructor looks like to the JVM:

Interview i1;
Interview(){
    super();
    i1 = new Interview(); // this line calls the constructor
    System.out.println("Hello");
}

Answer 2

Your Interview i1 = new Interview(); says that each Interview has its own Interview object that belongs to it, and so once you call new Interview() in main , the system starts trying to create a new Interview for that one, and a new Interview for that one...

It never even makes it to the (explicit) constructor, because the system goes off on a never-ending chain of new Interview s first. You should almost certainly remove the i1 field from the Interview class.

Answer 3

You're creating a new Interview every time you instantiate an Interview . This leads to a never-ending cycle of constructor calls and instantiations, which eventually run out your stack space (because the function calls take stack space).

Note that if you had infinite stack space available to you, you would eventually fail from all the Interview objects being allocated on the heap.

Answer 4

因为一旦你在main()初始化第一个Interview() ，它就会创建并初始化第二个Interview ，它会创建并初始化另一个，等等。

Answer 5

All initialization you do at the fields would become the part of the parameter-less constructor(in your case).

So,your code would become

public class Interview 
{

    Interview i1;
    Interview()
    {
        super();//by default calls the constructor of Object
        i1 = new Interview();//initialization becomes part of constructor
        System.out.println("Hello");
    }

}

Now this would recursively instatiate Interview causing exception