java里把list转换成string再传回去

public String showBidGlance(){
       projectTeams=showProjectBidService.showBidGlance(start, 5, projectId);
        showCrews= showProjectBidService.showCrew(projectId);
        
        showCrews1= Pinjie();
        
      
    
        return "success";
    }
    public String Pinjie(){
        StringBuilder str= new StringBuilder();
        
        for(int i=0;i<showCrews.size();i++){
         if(i==showCrews.size()-1){
             str.append(showCrews.get(i));
             }
             else{
             str.append(showCrews.get(i));
                 str.append(",");
         }
        }
        //System.out.println(str);
        return str.toString();
    }
这是一段代码，我想要把showCrews通过Pinjie（）这个方法将list型数据showCrews拼接转换为string型再返回给上面方法自己定义的showcrews1应该怎么做？其中showcrews在数据库搜索出来是两个姓名

补充：Java ,  Eclipse