java - 无法关闭我的文件

Question

我使用 Formatter 创建我的文件，当我尝试关闭它时，finally block 它说实例变量尚未初始化，但是如果我在 try block 中关闭它，它会起作用，但我不想这样做。另外，附注，我也不知道我是否正确使用了异常，因为我不知道其中两个是什么。

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，这是我在评论后得到的:

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();
      }
    }
    }
 }

这是错误:变量文件可能尚未初始化

Answer 1

只需更改 final Formatter file;至

Formatter file = null;

请注意，我不相信这可以是 final为此，编译器将看到文件变量将被初始化为某些内容。

然后在最后检查是否为 null:

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

<小时/>

编辑
或者根据 MadProgrammer，使用 Java 7 的 try 资源。

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.");
}