Answers クラス

public class FindSimilarQuestionController {

   public static void test() {
   // Instantiate a new question 
   Question question = new Question ();

   // Specify a title for the new question
   question.title = 'How much vacation time do full-time employees get?';

   // Specify the communityID (INTERNAL_COMMUNITY) in which to find similar questions. 
   Community community = [ SELECT Id FROM Community WHERE Name = 'INTERNAL_COMMUNITY' ];

   question.communityId = community.id;

   ID[] results = Answers.findSimilar(question);
   }
}

ID questionId = [SELECT Id FROM Question WHERE Title = 'Testing setBestReplyId' LIMIT 1].Id;
ID replyID = [SELECT Id FROM Reply WHERE QuestionId = :questionId LIMIT 1].Id;
Answers.setBestReply(questionId,replyId);