How to create a Binary Tree using a String array? - data-structures

Question

I am given an assignment where I need to do the following:
input your binary tree as an array, using the array representation and node labels A, ..., J, as Strings. Label null stands for a non-existent node, not for a node having a value of null.
Check the validity of your binary tree input: each node, excepting the root, should have a father.
Generate the dynamic memory implementation of the tree, using only the nodes with labels different than null.
So far I have:
public class Project1{
public static void main(String[] args){
String[] input = new String[]{"A","B","C","D","E","F","G","H","I","J"};
}
public class BinaryTree<T> implements java.io.Serializable{
private T data;
private BinaryTree<T> left;
private BinaryTree<T> right;
public BinaryTree(T data){
this.data = data;
left = null;
right = null;
}
public T getData(){
return data;
}
public void attachLeft(BinaryTree<T> tree){
if(tree != null){
left = tree;
}
}
public void attachRight(BinaryTree<T> tree){
if(tree != null){
right = tree;
}
}
public BinaryTree<T> detachLeft(){
BinaryTree<T> t = left;
left = null;
return t;
}
public BinaryTree<T> detachRight(){
BinaryTree<T> t = right;
right = null;
return t;
}
public boolean isEmpty(){
return data == null;
}
public void inOrder(BinaryTree<T> tree){
if (tree != null){
inOrder(tree.left);
System.out.println(tree.getData());
inOrder(tree.right);
}
}
public void preOrder(BinaryTree<T> tree){
if(tree != null){
System.out.println(tree.getData());
preOrder(tree.left);
preOrder(tree.right);
}
}
public void postOrder(BinaryTree<T> tree){
if(tree != null){
postOrder(tree.left);
postOrder(tree.right);
System.out.println(tree.getData());
}
}
}
What I don't understand is how to create a BinaryTree using my data from the string array