Sample usage of @fieldmap option for the Retrofit library

FieldMapUsageExample.java

public interface ApiService {
    
     @FormUrlEncoded
     @POST("/endpoint")
     Call<ReturnType> method(@FieldMap Map<String, String> fields);
}

public void sampleUsage {
    
    Map<String, String> map = new HashMap<>();
    map.add(requiredParam1Name, requiredParam1Value);
    map.add(optionalParam1Name, optionalParam1Value);
    map.add(optionalParam2Name, optionalParam2Value);
    
    Call<ReturnType> returnedObject = apiService.method(map);
}