异常IOException从不在相应try语句的正文中抛出

Question

我不是太笨，不会意识到“try catch”中的代码不能抛出异常。但是我被困在这里，因为我完全从书中复制了代码，所以它在出版时肯定是正确的。这让我想知道代码是否不能再编译了，因为它已经过时了？我意识到这个问题的性质可能会冒犯在座的一些人。如果是的话，请不要在严厉的斥责中过于严厉。

我得到了一个错误：

./streamcopier.java：13：错误：异常IOException从不在相应try语句的正文中抛出}catch（IOException e）{system.err.println(e)；}

//FileTyper.java
//Reads filenames from the command line and copies named files onto System.out.

import java.io.*;

public class FileTyper  {

  public static void main (String[] args)  {

    if (args.length == 0)  {
      System.err.print("usage: java FileTyper file1, file2");
      return;
    }

    for (int i = 0 ; i < args.length ; i++)  {
      try  {
        typeFile(args[i]);
        if (i+1 < args.length)  {    //more files waiting to be processed
          System.out.println();
          System.out.println("********************************************");
        }
      } catch (IOException e) {System.err.println(e);}
    } //end for

  } //end main()

  public static void typeFile (String filename) throws IOException  {

    FileInputStream fin = new FileInputStream(filename);
    StreamCopier.copy(fin, System.out);
    fin.close();
  }
}


//StreamCopier.java
//hard to know what this program does exactly

import java.io.*;

public class StreamCopier  {

  public static void main (String[] args)  {

    try  {

    } catch (IOException e) {System.err.println(e);}

  }

  public static void copy (InputStream in, OutputStream out) throws IOException  {

    //do not allow other threads to read from the  input or
    //write to the output while copying is taking place.
    synchronized (in)  {
      synchronized (out)  {
        byte [] buffer = new byte [256];
        while (true) {
          int bytesRead = in.read(buffer);
          if (bytesRead == -1) break;
          out.write(buffer, 0, bytesRead);
        }
      }
    }

  }  //end copy()

} 

Answer 1

该错误是由于StreamCopier.java的main方法中的try{}catch{}块为空。删除空的try{}catch{}块，然后尝试。应该管用。

public static void main (String[] args)  {
            try  {


            } catch (IOException e) {System.err.println(e);} // here is the problem
}