Same Tree LeetCode

https://oj.leetcode.com/problems/same-tree/

    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;    }