Maximum Number of Pairs in Array LeetCode solution in Java

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class Solution {
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  public int[] numberOfPairs(int[] nums) {
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    if (nums.length == 1) return new int[] {0, 1};
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    HashSet<Integer> set = new HashSet<>();
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    int pairs = 0;
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    for (int i : nums) {
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      if (!set.contains(i)) {
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        set.add(i); // No pair present
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      } else {
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        set.remove(i); // Pair found
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        pairs++;
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      }
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    }
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    return new int[] {pairs, set.size()};
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  }
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}