Explain what a hierarchical table structure is and what are its advantages.

A hierarchical table is a data structure that organizes elements in a tree-like form, where each element (node) can have one parent and multiple children. In the context of databases or Java, this is often implemented through references to the parent element or nested collections.

Advantages of a hierarchical table:

• Natural representation of data with hierarchy (e.g., categories, subdivisions).
• Simplifies navigation and search within the structure.
• Easy to add and remove nodes without breaking integrity.

An example in Java — a class representing a node with a reference to its parent and a list of children:

class TreeNode {
    String name;
    TreeNode parent;
    List<TreeNode> children = new ArrayList<>();

    public TreeNode(String name) {
        this.name = name;
    }

    public void addChild(TreeNode child) {
        child.parent = this;
        children.add(child);
    }
}