How to create own tree in java? [duplicate]

You'll probably need to create some sort of Node class to represent the nodes in the tree:

public class Node
{
    private List<Node> children = null;
    private String value;

    public Node(String value)
    {
        this.children = new ArrayList<>();
        this.value = value;
    }

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

}

Then to populate your tree:

public static void main(String [] args)
{
    Node root = new Node("root");
    root.addChild(new Node("child1"));
    root.addChild(new Node("child2")); //etc.
}

You'll have to modify this to suit your own purposes, this code is just to give you an idea of the structure.

A good design will be : Create a class RootNode with array of eight references to another class FirstLevelChildNode which in turn has dynamic array (say ArrayList) of another class ChildNodes, with required operations in each class...