Use appropriate collections

Choose the right collection implementation for each algorithmic task to optimize both performance and readability. Use Sets for operations requiring uniqueness, TreeMap for maintaining sorted keys, and leverage built-in collection methods rather than implementing operations manually.

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Choose the right collection implementation for each algorithmic task to optimize both performance and readability. Use Sets for operations requiring uniqueness, TreeMap for maintaining sorted keys, and leverage built-in collection methods rather than implementing operations manually.

Key practices:

  • Use HashSet instead of List+contains checks when eliminating duplicates
  • Prefer Map.computeIfAbsent over get-check-put patterns
  • Use specialized collection methods like Collections.addAll or direct List.sort instead of chained operations
  • Select TreeMap when sorted key access is required

Example of improvement:

// Less efficient approach
List<String> items = new ArrayList<>();
items.addAll(Arrays.asList(array1));
for (String item : array2) {
    if (!items.contains(item)) {  // O(n) operation for each check
        items.add(item);
    }
}

// More efficient approach
Set<String> uniqueItems = new LinkedHashSet<>();
Collections.addAll(uniqueItems, array1);
Collections.addAll(uniqueItems, array2);  // Duplicates automatically handled

Another optimization example:

// Less efficient sorting
Collections.sort(advisors, new OrderComparator());

// More efficient sorting
advisors.sort(OrderComparator.INSTANCE);  // Or OrderComparator.sort(advisors)

This approach improves algorithmic efficiency by selecting data structures with appropriate time complexity for the required operations.

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