base/common/src/main/com/thesett/common/util/SimpleTree.java
public void addChild(Tree<E> child)
    {
        initChildren();

        // Add the new child to the collection of children.
        children.add(child);

        // Set the type of this point in the tree to a node as it now has children.
        nodeOrLeaf = Type.Node;

        // Set the new childs parent to this.
        child.setParent(this);
    }
public void addChild(Tree<E> child)
    {
        initChildren();

        // Add the new child to the collection of children.
        children.add(child);

        // Set the type of this point in the tree to a node as it now has children.
        nodeOrLeaf = Type.Node;

        // Set the new childs parent to this.
        child.setParent(this);
    }
Adds a child tree to the children of this point in the tree. If this is already a node then it remains as a node.
If this is a leaf then adding a child to it must promote it to become a node. This implementation supports
turning leaves into nodes.

@param child A child tree to add below this point in the tree.