Write a method that takes a List<Integer> and returns the second largest unique number in the list. If there is no second largest number (the list has fewer than 2 unique numbers), return null.

Requirements

  • Find the second largest unique value
  • Handle duplicates correctly - they do not count as separate values
  • Return null if there are not at least 2 unique numbers
  • Handle null or empty lists by returning null

Examples

findSecondLargest(new List<Integer>{1, 2, 3, 4, 5})
// Returns: 4
// Explanation: Largest is 5, second largest is 4

findSecondLargest(new List<Integer>{10, 10, 10})
// Returns: null
// Explanation: Only one unique number (10)

findSecondLargest(new List<Integer>{5, 5, 3})
// Returns: 3
// Explanation: Unique values are [5, 3], second largest is 3

findSecondLargest(new List<Integer>{1})
// Returns: null
// Explanation: Only one number in list

findSecondLargest(new List<Integer>{})
// Returns: null
// Explanation: Empty list

findSecondLargest(null)
// Returns: null
// Explanation: Null list
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