Friends Of Appropriate Ages LeetCode solution in Java

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class Solution {
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  static int upperBound(int arr[], int target) {
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    int l = 0, h = arr.length - 1;
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    for (; l <= h; ) {
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      int mid = (l + h) >> 1;
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      if (arr[mid] <= target) l = mid + 1;
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      else h = mid - 1;
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    }
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    return l;
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  }
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  public int numFriendRequests(int[] ages) {
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    long ans = 0;
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    Arrays.sort(ages);
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    // traversing order doesn't matter as we are doing binary-search in whole array
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    // you can traverse from left side also
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    for (int i = ages.length - 1; i >= 0; --i) {
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      int k = upperBound(ages, ages[i] / 2 + 7);
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      int t = upperBound(ages, ages[i]);
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      ans += Math.max(0, t - k - 1);
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    }
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    return (int) ans;
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  }
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}