Tree implementation in Java (root, parents and children)

Question

I need to create a tree structure similar as the attached image in Java. I\'ve found some questions related to this one but I haven\'t found a convincing and well explained

Answer 1

import java.util.ArrayList;
import java.util.List;

public class Node {
    private List> children = new ArrayList>();
    private Node parent = null;
    private T data = null;

    public Node(T data) {
        this.data = data;
    }

    public Node(T data, Node parent) {
        this.data = data;
        this.parent = parent;
    }

    public List> getChildren() {
        return children;
    }

    public void setParent(Node parent) {
        parent.addChild(this);
        this.parent = parent;
    }

    public void addChild(T data) {
        Node child = new Node(data);
        child.setParent(this);
        this.children.add(child);
    }

    public void addChild(Node child) {
        child.setParent(this);
        this.children.add(child);
    }

    public T getData() {
        return this.data;
    }

    public void setData(T data) {
        this.data = data;
    }

    public boolean isRoot() {
        return (this.parent == null);
    }

    public boolean isLeaf() {
        return this.children.size == 0;
    }

    public void removeParent() {
        this.parent = null;
    }
}

Example:

import java.util.List;

Node parentNode = new Node("Parent"); 
Node childNode1 = new Node("Child 1", parentNode);
Node childNode2 = new Node("Child 2");     

childNode2.setParent(parentNode); 

Node grandchildNode = new Node("Grandchild of parentNode. Child of childNode1", childNode1); 
List> childrenNodes = parentNode.getChildren();