AVL tree balancing

Question

I am working on a task that asks me to implement an AVL tree. I'm sure I have the right rotation methods, but it's hard for me to figure out when to use them.

For example, the explanation in the book says that I have to go up the same path that I went to insert the node / element. However, I cannot have any parent pointers.

Last code:

public BinaryNode<T> insert(BinaryNode<T> node) {
    if (this.getElement().compareTo(node.getElement()) > 0) {
        if (this.getLeftChild() != null) {
            BinaryNode<T> b = this.getLeftChild().insert(node);

            if(!this.isBalanced()) {
                this.balance();
            }

            return b;
        } else {
            this.setLeftChild(node);
        }

    } else if (this.getElement().compareTo(node.getElement()) < 0) {
        if (this.getRightChild() != null) {
            return this.getRightChild().insert(node);
        } else {
            this.setRightChild(node);
        }
    }

    return this;
}

What I want to do is climb the tree, but it can only check the balance AFTER it inserts the node. Therefore, this is in the else clause.

I also tried to enter the balance code, where I suggested R Samuel Klatchko, but checked the balance on each tab. For example: if you insert 7, 9, 5, 3, and 1 sequentially, I get a null pointer exception when trying to insert 1.

EDIT: - , . , (), O (log (n)) AVL.

, ?

Answer 1

, . :

if (this.getLeftChild() != null) {
    return this.getLeftChild().insert(node);
} 

:

if (this.getLeftChild() != null) {
    boolean b = this.getLeftChild().insert(node);
    // do something here
    return b;
} 

, . , .

, .

Answer 2

insert insert , .

, , , , node , , . , isBalanced . AVL tree O (log n), .