Leaf-Similar Trees LeetCode solution in Java

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class Solution {
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  public boolean leafSimilar(TreeNode root1, TreeNode root2) {
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    List<Integer> list1 = new ArrayList<>();
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    checkLeaf(root1, list1);
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    List<Integer> list2 = new ArrayList<>();
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    checkLeaf(root2, list2);
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    if (list1.size() != list2.size()) return false;
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    int i = 0;
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    while (i < list1.size()) {
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      if (list1.get(i) != list2.get(i)) {
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        return false;
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      }
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      i++;
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    }
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    return true;
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  }
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  private void checkLeaf(TreeNode node, List<Integer> arr) {
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    if (node.left == null && node.right == null) arr.add(node.val);
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    if (node.left != null) checkLeaf(node.left, arr);
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    if (node.right != null) checkLeaf(node.right, arr);
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  }
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}