我创造的这个方法

public class Use {
    private
    String firstname;
     String lastname;
     
     public String output() {
            return "Hii my name is " + firstname + lastname;
        }   
            public String getFirstName() {
                return firstname.toUpperCase();
            }
            public void setFirstName(String jl) {
                firstname = jl.strip() ;
                
            }
            public String getLastName() {
                return lastname.toUpperCase();
                
            }
            public void setLastName(String FN) {
                lastname = FN.strip();
            }
            
    }

我尝试在下面的代码中使用上面的方法：

import java.util.ArrayList;
import java.util.List;

public class MySweetProgram {

    public static void main(String[] args) {
        String[] firstnames = {"KARRIK", "KESHAV", "Sussy"};
        String[] lastnames = {"gulati", "gulati", "smith"};
        List <User> users = new ArrayList<User>();
    
        for (int  i = 0; i < firstnames.length;     i ++) {
        User user = new User();
        user.setFirstName(firstnames[i]);
        user.setLastName(lastnames[i]);
        users.add(user);
        } 
    for (User user : users) {
        System.out.println(user.getfullname());
    }       
   }
    
}

运行时获取null null