Write a method that checks if a binary tree is perfect

public Boolean isPerfectTree(TreeNode node) {
 int treeDepth = depth(node);
    return isPerfectTree(node, 1, treeDepth);
}

private int depth(TreeNode node) {
    return node.left() != null ? 1 + depth(node.left()) : 1;
}

private Boolean isPerfectTree(TreeNode node, int depth, int treeDepth) {
    // check for last level node
    if (depth == treeDepth && (node.left() == null && node.right() == null)) {
        return true;
    }
    // check for inner levels
    if ((node.left() != null && node.right() != null)) {
        return isPerfectTree(node.left(), 1 + depth, treeDepth) &&
                isPerfectTree(node.right(), 1 + depth, treeDepth);
    }
    return false;
}