Referencing Parent Arraylist from Within Arraylist in Java

So I was wondering if it was possible in Java to trace back up an Array List? Meaning, if I have something like:

Section aSection = new Section();
aMainSection.get(0).aChildSection.add(aSection);

Where 'aMainSection' and 'aChildSection' are both Array Lists开发者_Python百科 of type section, can I trace back up from 'aChildSection' to get the values stored in it's parent section 'aMainSection'? Or do I have to create some sort of method within the section class that will do this? Thanks for any help that is offered.

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You cannot find all the references to an object from the object itself. You can instead record a "parent" Object in each of the children.

Instead of exposing the raw collections you may way to have custom classes for them.

class ChildSection {
    private final Section parent;
    private final List<Section> sections = new ArraysList<Section>();

    public void add(Section section) {
        sections.add(section);
        section.setParent(parent);
    }
}

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No, you can't track upwards with ArrayLists, you will have to add parent references in each Section object.