Number of Pairs of Interchangeable Rectangles LeetCode solution in Java

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class Solution {
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  public long interchangeableRectangles(int[][] rectangles) {
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    Map<Double, Long> hash = new HashMap<>();
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    for (int i = 0; i < rectangles.length; i++) {
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      Double tmp = (double) (rectangles[i][0] / (double) rectangles[i][1]);
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      hash.put(tmp, hash.getOrDefault(tmp, 0L) + 1);
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    }
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    long ans = 0;
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    for (Map.Entry<Double, Long> entry : hash.entrySet()) {
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      if (entry.getValue() > 1) {
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        Long n = entry.getValue();
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        ans += (n * (n - 1)) / 2;
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      }
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    }
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    return ans;
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  }
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}