java - 变量 g 可能尚未初始化

Question

我对我正在从事的这个项目有很多疑问。这是电影的虚拟数据库。我有一个小型 MovieEntry 类(用于处理单个条目)和一个大型 MovieDatabase 类，用于跟踪所有 10k+ 条目。在我的第二个 searchYear 方法以及后续方法中，我收到错误“变量 g(或 d 或其他)可能尚未初始化。”我还收到一个弹出错误，显示 Warnings from last Compilation: unreachable catch Clause。抛出的类型 java.io.FileNotFoundException 已经被捕获。 我对这两个问题都感到困惑。代码如下:

public class MovieDatabase
{
   private ArrayList<MovieEntry> Database = new ArrayList<MovieEntry>();
   public MovieDatabase(){
       ArrayList<MovieDatabase> Database = new ArrayList<MovieDatabase>(0);
    }

   public int countTitles() throws IOException{
       Scanner fileScan;
       fileScan = new Scanner (new File("movies.txt"));
       int count = 0;
       String movieCount;
       while(fileScan.hasNext()){
           movieCount = fileScan.nextLine();
           count++;
        }
       return count;
    }

   public void addMovie(MovieEntry m){
       Database.add(m);
    }

   public ArrayList<MovieEntry> searchTitle(String substring){
       for (MovieEntry title : Database)
          System.out.println(title);
          return null;
    }

   public ArrayList<MovieEntry> searchGenre(String substring){
       for (MovieEntry genre : Database)
          System.out.println(genre);
          return null;
    }

   public ArrayList<MovieEntry> searchDirector (String str){
       for (MovieEntry director : Database)
          System.out.println(director);
       return null;
    }

   public ArrayList<String> searchYear (int yr){
       ArrayList <String> yearMatches = new ArrayList<String>();
       for (MovieEntry m : Database)
          m.getYear(yr);
       if(yearMatches.contains(yr) == false){
           String sYr = Integer.toString(yr);
           yearMatches.add(sYr);
        }
       return yearMatches;
    }

   public ArrayList<MovieEntry> searchYear(int from, int to){
       ArrayList <String> Matches = new ArrayList<String>();
       for(MovieEntry m : Database);
          m.getYear();
          Matches.add();
       return Matches;
    }

   public void readMovieData(String movies){
       String info;
       try{
           Scanner fileReader = new Scanner(new File("movies"));
           Scanner lineReader;

           while(fileReader.hasNext()){
               info = fileReader.nextLine();

               lineReader = new Scanner(info);
               lineReader.useDelimiter(":");

               String title = lineReader.next();
               String director = lineReader.next();
               String genre = lineReader.next();
               int year = lineReader.nextInt();
            }

        }catch(FileNotFoundException error){
            System.out.println("File not found.");

        }catch(IOException error){
            System.out.println("Oops! Something went wrong.");
        }
    }

   public int countGenres(){
    ArrayList <String> gList = new ArrayList<String>();
    for(MovieEntry m : Database){
      String g = m.getGenre(g);
      if(gList.contains(g) == false){
        gList.add(g);
      }
      return gList.size();
    }
    }

    public int countDirectors(){
     ArrayList <String> dList = new ArrayList<String>();
     for(MovieEntry m : Database){
        String d = m.getDirector(d);
        if(dList.contains(d) == false){
            dList.add(d);
        }
        return dList.size();
     }

     }

    public String listGenres(){
        ArrayList <String> genreList = new ArrayList<String>();
    }




}

Answer 1

catch(IOException error){
            System.out.println("Oops! Something went wrong.");
        }

它告诉您 FileNotFoundException将处理 IOException 正在捕获的内容，因此 IOException 变得无法访问，因为它永远不会捕获 IO exceltion，为什么不捕获 Exception相反

至于初始化

public int countDirectors(){
     ArrayList <String> dList = new ArrayList<String>();
     for(MovieEntry m : Database){
        String d = m.getDirector(d);  //THIS LINE
        if(dList.contains(d) == false){
            dList.add(d);
        }
        return dList.size();
     }

线路String d = m.getDirector(d);可能是问题所在，d除非 MovieEntry 中有东西，否则不会被初始化，据我所知，永远不会有任何东西，因为您将其初始化为空数组列表

ArrayList<MovieDatabase> Database = new ArrayList<MovieDatabase>(0);

也许您应该将电影数组传递给构造函数，然后将这些电影添加到 Database变量？