Print words contained in binary tree

Starting from the next binary tree, I should print the words it may contain on the screen, with a line break between them.

I have obtained functions like going through all the nodes to add their content or simply count the nodes, but I do not understand how to print each word always starting with the main root (letter B) and reusing letters

Function number of nodes:

public static int numNodos(Arbol a) {
    if (a.esVacio()) {
        return 0;
    } else {
        return 1 + numNodos(a.hijoIzq) + numNodos(a.hijoDcho());
    }
}

Tree depth function:

public static int profundidad(Arbol a, int maxprof) {
    if (a.esVacio()) {
        return maxprof;
    } else {
        return Math.Max(profundidad(a.hijoIzq(), maxprof + 1), profundidad(a.hijoDcho(), maxprof + 1));
    }
}