Leaf-Similar Trees

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    private static void solve(TreeNode root, ArrayList<Integer> ans) {
        if(root.left == null && root.right == null) {
            ans.add(root.val);
        }
        
        if(root.left != null) solve(root.left, ans);
        if(root.right != null) solve(root.right, ans);
        
    }
    
    public boolean leafSimilar(TreeNode root1, TreeNode root2) {
        if(root1 == null && root2 == null) return true;
        if(root1 == null || root2 == null) return false;
        ArrayList<Integer> ans1 = new ArrayList<>();
        solve(root1, ans1);
        // System.out.println(ans1);
        ArrayList<Integer> ans2 = new ArrayList<>();
        solve(root2, ans2);
        // System.out.println(ans2);
        return ans1.equals(ans2);
    }
}