無法關閉我的文件

Question

我使用Formatter創建了文件，當我嘗試關閉它的finally塊時，它說實例變量尚未初始化，但是如果我在try塊中將其關閉，它可以工作，但是我不想這樣做。 另外，請注意，我也不知道我是否正確使用了我的異常，因為我不知道它們是什么兩個。

public class NewFile
{
 public static void main(String[] args)
 {

final Formatter file;

    try// create file
    {
    file = new Formatter("Records.txt");

     Account[] records = new Account[4];

      records[ 0 ] = new Account( 100, "January", "Smith", 34.56 );
      records[ 1 ] = new Account( 200, "Sally", "Anderson", 467.10 );
      records[ 2 ] = new Account( 300, "Joe", "Wright", -67.60 );
      records[ 3 ] = new Account( 400, "Henry", "Hein", 0.00 );


   for(Account display : records)
       {
      file.format("\n %d %s %s %,.2f\n", display.getAccount(),display.getFirst(), display.getLast(), display.getBalance());
   }
    }

   catch(FileNotFoundException fileNotFoundException)
    {
      System.err.println("File not found.");
    }
      catch(SecurityException securityException)
    {
      System.err.println("Do not have required permission.");
    }

       catch(FormatterClosedException formatterClosedException)
    {
      System.err.println("File is already closed.");
    }

    catch(IllegalStateException illegalStateException)
    {
      System.err.println("Error reading from file.");
    }

    finally//close the file
    {
    file.close();
    }
 }

好的，這是我在評論后所擁有的：

import java.util.Formatter;
import java.io.FileNotFoundException;
import java.lang.IllegalStateException;
import java.lang.SecurityException;
import java.util.FormatterClosedException;

public class NewFile
{
 public static void main(String[] args)
 {

 Formatter file;

    try// create file
    {
    file = new Formatter("Records.txt");

     Account[] records = new Account[4];

      records [ 0 ] = new Account( 100, "January", "Smith", 34.56 );
      records[ 1 ] = new Account( 200, "Sally", "Anderson", 467.10 );
      records[ 2 ] = new Account( 300, "Joe", "Wright", -67.60 );
      records[ 3 ] = new Account( 400, "Henry", "Hein", 0.00 );


   for(Account display : records)
       {
      file.format("\n %d %s %s %,.2f\n", display.getAccount(),display.getFirst(), display.getLast(), display.getBalance());
   }
    }

   catch(FileNotFoundException fileNotFoundException)
    {
      System.err.println("File not found.");
    }
      catch(SecurityException securityException)
    {
      System.err.println("Do not have required permission.");
    }

       catch(FormatterClosedException formatterClosedException)
    {
      System.err.println("File is already closed.");
    }

    catch(IllegalStateException illegalStateException)
    {
      System.err.println("Error reading from file.");
    }

    finally//close the file
    {
      if(file != null)
      {
    file.close();
      }
    }
    }
 }

這是錯誤：變量文件可能尚未初始化

Answer 1

只需更改final Formatter file; 至

Formatter file = null;

請注意，我不認為這可以是final的，但是通過這種方式，編譯器將看到文件變量將被初始化為某種東西。

然后，最后檢查null：

finally {
   if (file != null) {
      file.close();
   }
}

---

編輯
或按照MadProgrammer的要求，對資源使用Java 7的try。

try (Formatter file = new Formatter("Records.txt")) {
    // do stuff with file here

} catch(FileNotFoundException fileNotFoundException) {
      System.err.println("File not found.");
} catch(SecurityException securityException) {
      System.err.println("Do not have required permission.");
} catch(FormatterClosedException formatterClosedException) {
      System.err.println("File is already closed.");
} catch(IllegalStateException illegalStateException) {
      System.err.println("Error reading from file.");
}

Answer 2

這段代碼為我編譯（我不得不捏造Account類）：

public class NewFile
{
    public static void main(String[] args)
    {
        Formatter file = null;
        try
        // create file
        {
            file = new Formatter("Records.txt");

            Account[] records = new Account[4];

            records[0] = new Account(100, "January", "Smith", 34.56);
            records[1] = new Account(200, "Sally", "Anderson", 467.10);
            records[2] = new Account(300, "Joe", "Wright", -67.60);
            records[3] = new Account(400, "Henry", "Hein", 0.00);

            for (Account display : records)
            {
                file.format("\n %d %s %s %,.2f\n", display.getAccount(), display.getFirst(), display.getLast(),
                            display.getBalance());
            }
        }

        catch (final FileNotFoundException fileNotFoundException)
        {
            System.err.println("File not found.");
        }
        catch (final SecurityException securityException)
        {
            System.err.println("Do not have required permission.");
        }

        catch (final FormatterClosedException formatterClosedException)
        {
            System.err.println("File is already closed.");
        }

        catch (final IllegalStateException illegalStateException)
        {
            System.err.println("Error reading from file.");
        }

        finally
        // close the file
        {
            if (file != null)
            {
                file.close();
            }
        }
    }
}