Display Table of Food Orders in a Restaurant LeetCode solution in Java

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class Solution {
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  public List<List<String>> displayTable(List<List<String>> orders) {
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    List<List<String>> ans = new ArrayList<>();
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    List<String> head = new ArrayList<>();
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    head.add("Table");
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    Map<Integer, Map<String, Integer>> map = new TreeMap<>();
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    for (List<String> s : orders) {
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      if (!head.contains(s.get(2))) head.add(s.get(2));
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      int tbl = Integer.parseInt(s.get(1));
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      map.putIfAbsent(tbl, new TreeMap<>());
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      if (map.get(tbl).containsKey(s.get(2))) {
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        Map<String, Integer> m = map.get(tbl);
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        m.put(s.get(2), m.getOrDefault(s.get(2), 0) + 1);
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      } else {
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        map.get(tbl).put(s.get(2), 1);
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      }
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    }
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    String[] arr = head.toArray(new String[0]);
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    Arrays.sort(arr, 1, head.size());
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    head = Arrays.asList(arr);
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    ans.add(head);
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    for (Map.Entry<Integer, Map<String, Integer>> entry : map.entrySet()) {
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      List<String> l = new ArrayList<>();
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      l.add(entry.getKey() + "");
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      Map<String, Integer> m = entry.getValue();
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      for (int i = 1; i < arr.length; i++) {
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        if (m.containsKey(arr[i])) {
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          l.add(m.get(arr[i]) + "");
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        } else {
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          l.add("0");
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        }
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      }
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      ans.add(l);
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    }
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    System.out.print(map);
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    return ans;
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  }
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}