import java.util.HashSet;

import java.util.Map;

import java.util.Set;

import java.util.HashMap;

public class DuplicateRemover {

/**

* Removes duplicate form field values from a map of field names to values.

* Handles potential null values gracefully.

*

* @param formFields A map where keys are form field names (Strings) and values are field values (Strings).

* @return A new map with duplicate values removed. Returns an empty map if the input is null.

*/

public static Map<String, String> removeDuplicateValues(Map<String, String> formFields) {

if (formFields == null) {

return new HashMap<>(); // Handle null input gracefully

}

Set<String> seenValues = new HashSet<>(); // Use a set to efficiently track seen values

Map<String, String> uniqueFields = new HashMap<>();

for (Map.Entry<String, String> entry : formFields.entrySet()) {

String fieldName = entry.getKey();

String fieldValue = entry.getValue();

if (fieldValue != null) { // Handle null values

if (!seenValues.contains(fieldValue)) {

uniqueFields.put(fieldName, fieldValue);

seenValues.add(fieldValue);

}

} else {

//If value is null, skip that field

//Alternatively, could store null in the unique map if desired.

}

}

return uniqueFields;

}

public static void main(String[] args) {

//Example Usage

Map<String, String> formData = new HashMap<>();

formData.put("name", "John");

formData.put("age", "30");

formData.put("city", "New York");

formData.put("occupation", "Engineer");

formData.put("age", "30"); // Duplicate age

formData.put("country", null);

formData.put("city", "London"); //Duplicate city

Map<String, String> uniqueData = removeDuplicateValues(formData);

System.out.println(uniqueData); //Output: {name=John, age=30, city=New York, occupation=Engineer, country=null}

}

}