Example: FindFirstNonRepeatingTraditional in Java

// FindFirstNonRepeatingTraditional
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Optional;

public class Main {
    public static Optional<Character> findFirstNonRepeatingTraditional(String s) {
        if (s == null || s.isEmpty()) {
            return Optional.empty();
        }

        // Step 1: Use LinkedHashMap to store character counts and preserve insertion order
        Map<Character, Integer> charCounts = new LinkedHashMap<>();
        for (char c : s.toCharArray()) {
            charCounts.put(c, charCounts.getOrDefault(c, 0) + 1);
        }

        // Step 2: Iterate through the map entries to find the first character with count 1
        for (Map.Entry<Character, Integer> entry : charCounts.entrySet()) {
            if (entry.getValue() == 1) {
                return Optional.of(entry.getKey());
            }
        }

        // Step 3: If no non-repeating character is found, return empty
        return Optional.empty();
    }

    public static void main(String[] args) {
        System.out.println("--- Traditional Approach ---");
        System.out.println("stress -> " + findFirstNonRepeatingTraditional("stress").orElse(null)); // t
        System.out.println("aabbc -> " + findFirstNonRepeatingTraditional("aabbc").orElse(null));   // c
        System.out.println("aabb -> " + findFirstNonRepeatingTraditional("aabb").orElse(null));     // null
        System.out.println("java -> " + findFirstNonRepeatingTraditional("java").orElse(null));     // j
        System.out.println(" -> " + findFirstNonRepeatingTraditional("").orElse(null));           // null
        System.out.println("zzzaac -> " + findFirstNonRepeatingTraditional("zzzaac").orElse(null)); // c
    }
}