Same Tree LeetCode

public boolean isSameTree(TreeNode p, TreeNode q) {
if(p==null&&q==null){
return true;
}
if(p==null){
return false;
}
if(q==null){
return false;
}
Stack<TreeNode> stackA= new Stack<TreeNode>();
Stack<TreeNode> stackB= new Stack<TreeNode>();

stackA.push(p);
stackB.push(q);

while(!stackA.empty()&&!stackB.empty()){
TreeNode a= stackA.pop();
TreeNode b= stackB.pop();

if(a.val!=b.val){
return false;
}

if(a.left!=null){
if(b.left==null){
return false;
}
stackA.push(a.left);
stackB.push(b.left);
}else{
if(b.left!=null){
return false;
}
}
if(a.right!=null){
if(b.right==null){
return false;
}
stackA.push(a.right);
stackB.push(b.right);
}else{
if(b.right!=null){
return false;
}
}

}
return true;
}