Here is my code for ExtendedAVLNode.java and ExtendedAVLTree.java. and the results. I am receiving failed tests and I am not sure exactly where my code needs to be updated.

public class ExtendedAVLNode extends AVLNode $\{$

private int subtreeKeyCount;

public ExtendedAVLNode$($int nodeKey$)\{$

super$($nodeKey$)$;

this.subtreeKeyCount $=1$;

$\}$

public int getSubtreeKeyCount$()\{$

return subtreeKeyCount;

$\}$

public void updateSubtreeKeyCount$()\{$

int leftCount $=($getLeft$()!=$ null$)?(($ExtendedAVLNode$)$ getLeft$()).$getSubtreeKeyCount$()$ : $0$;

int rightCount $=($getRight$()!=$ null$)?(($ExtendedAVLNode$)$ getRight$()).$getSubtreeKeyCount$()$ : $0$;

this.subtreeKeyCount $=$ leftCount $+$ rightCount $+1$;

$\}$

@Override

public void setLeft$($BSTNode left$)\{$

super.setLeft$($left$)$;

updateSubtreeKeyCount$()$;

$\}$

@Override

public void setRight$($BSTNode right$)\{$

super.setRight$($right$)$;

updateSubtreeKeyCount$()$;

$\}$

$\}$

public class ExtendedAVLTree extends AVLTree $\{$

$//$ Each node in an ExtendedAVLTree is an ExtendedAVLNode

@Override

protected BSTNode makeNewNode$($int key$)\{$

return new ExtendedAVLNode$($key$)$;

$\}$

public void insert$($int key$)\{$

insert$($key$)$;

updateSubtreeCounts$(($ExtendedAVLNode$)$ getRoot$())$;

$\}$

public void remove$($int key$)\{$

remove$($key$)$;

updateSubtreeCounts$(($ExtendedAVLNode$)$ getRoot$())$;

$\}$

private void updateSubtreeCounts$($ExtendedAVLNode node$)\{$

if $($node $!=$ null$)\{$

node.updateSubtreeKeyCount$()$;

updateSubtreeCounts$(($ExtendedAVLNode$)$ node.getLeft$())$;

updateSubtreeCounts$(($ExtendedAVLNode$)$ node.getRight$())$;

$\}$

$\}$

@Override

public int getNthKey$($int n$)\{$

return getNthKey$(($ExtendedAVLNode$)$ getRoot$(),$ n$)$;

$\}$

private int getNthKey$($ExtendedAVLNode node, int n$)\{$

if $($node $==$ null$)\{$

throw new IllegalArgumentException$("$Invalid n$")$;

$\}$

int leftCount $=($node$.$getLeft$()!=$ null$)?(($ExtendedAVLNode$)$ node.getLeft$()).$getSubtreeKeyCount$()$ : $0$;

if $($n $<$ leftCount$)\{$

return getNthKey$(($ExtendedAVLNode$)$ node.getLeft$(),$ n$)$;

$\}$ else if $($n $==$ leftCount$)\{$

return node.getKey$()$;

$\}$ else $\{$

return getNthKey$(($ExtendedAVLNode$)$ node.getRight$(),$ n $-$ leftCount $-1)$;

$\}$

$\}$

$\}$

Test $1-$ insertion and getSubtreeKeyCount$()$

Inserting keys: $10,20,30,55,42,19,77$

PASS: Inorder key verification

Expected: $[10,19,20,30,42,55,77]$

Actual: $[10,19,20,30,42,55,77]$

PASS: Node with key $10$ has a subtree key count of $2$

PASS: Node with key $19$ has a subtree key count of $1$

FAIL: Node with key $20$ has a subtree key count of $5,$ but the expected subtree key count is $7$

PASS: Node with key $30$ has a subtree key count of $1$

FAIL: Node with key $42$ has a subtree key count of $3,$ but the expected subtree key count is $4$

PASS: Node with key $55$ has a subtree key count of $2$

PASS: Node with key $77$ has a subtree key count of $1$

Test $2-$ insertion, removal, and getSubtreeKeyCount$()$

Inserting keys: $86,75,23,30,98,67,53,9,19,58,14$

PASS: Inorder key verification

Expected: $[9,14,19,23,30,53,58,67,75,86,98]$

Actual: $[9,14,19,23,30,53,58,67,75,86,98]$

PASS: Node with key $9$ has a subtree key count of $2$

PASS: Node with key $14$ has a subtree key count of $1$

FAIL: Node with key $19$ has a subtree key count of $3,$ but the expected subtree key count is $4$

PASS: Node with key $23$ has a subtree key count of $1$

FAIL: Node with key $30$ has a subtree key count of $10,$ but the expected subtree key count is $11$

PASS: Node with key $53$ has a subtree key count of $1$

PASS: Node with key $58$ has a subtree key count of $3$

PASS: Node with key $67$ has a subtree key count of $1$

PASS: Node with key $75$ has a subtree key count of $6$

PASS: Node with key $86$ has a subtree key count of $2$

PASS: Node with key $98$ has a subtree key count of $1$

Test $3-$ insertion, removal, getSubtreeKeyCount$(),$ and getNthKey$()$

Inserting keys: $10,58,66,18,34,96,5,48,73,62,36,16,23,99,92,95,46,97$

PASS: Inorder key verification

Expected: $[5,10,16,18,23,34,36,46,48,58,62,66,73,92,95,96,97,99]$

Actual: $[5,10,16,18,23,34,36,46,48,58,62,66,73,92,95,96,97,99]$

FAIL: getNthKey$(11)$ returned $95,$ but expected key is $66$

Summary:

Test $1$: FAIL

Test $2$: FAIL

Test $3$: FAIL