Count Good Meals LeetCode solution in Java

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class Solution {
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  int mod = 1000000007;
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  public int countPairs(int[] arr) {
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    Map<Integer, Integer> map = new HashMap<>();
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    int n = arr.length;
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    long res = 0;
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    for (int num : arr) {
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      int power = 1;
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      for (int i = 0; i < 22; i++) {
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        if (map.containsKey(power - num)) {
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          res += map.get(power - num);
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          res %= mod;
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        }
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        power *= 2;
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      }
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      map.put(num, map.getOrDefault(num, 0) + 1);
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    }
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    return (int) res;
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  }
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}