cannot be resolved to a variable 问题

public static ArrayList<String> readFile(File inputFile){
    try{
      Scanner in = new Scanner(inputFile);
      ArrayList<String> codes = new ArrayList<String>();
      while(in.hasNextLine()){
        codes.add(in.nextLine());
      }
      in.close();
    }catch(IOException exception){
      exception.printStackTrace();
    }catch(NoSuchElementException exception){
      System.out.println(exception.getMessage());
    }catch(Exception exception){
      System.out.println(exception.getMessage());
    }
    return codes;
  }

这段代码为何报错 codes cannot be resolved to a variable.（return那一行）

codes的生命期只限于try里面，提到前面就行了：
ArrayList<String> codes = null;
try里面直接给codes赋值