Question

In a Java file, I have the following code:

MyTree atree = new MyTree();
atree.insert(1);

This is not a regular tree. “atree” is the root node. Every node in this tree has 5 children, all initially set to null. The parameter for insert is the child that you want to ‘activate’, that is, make it non-null. So I have a method in the MyTree class that does this:

public void insert(int i)
{
    if(i == 1)
    {
        MyTree current = this.getChildOne();
        current = new MyTree();
    }
}

After I call the function, I check the first node in the file where I called it.

if(atree.getChildOne() == null)
{
    return -1;
}

And it always returns negative one. I suspect that the insert function is actually working on a copy of ‘atree’ and not the actual ‘atree’. But I am not entirely sure. Anyone have an explanation?

Answer 1

It doesn’t look like you are assigning child one anywhere. The code

MyTree current = this.getChildOne();
current = new MyTree();

does not assign child one. You initialize a local variable current but then that variable is lost when the method ends.

I think you probably want to do something like this in your insert method

if ( i == i ) {
   this.childOne = // assign it here
}