Can I miss the catch clause to throw exception to its caller?

Question

What kind of problem may occur for this code? I think even exception occurs, this code can throw the exception to its caller. So it does NOT generate any trouble.

How can I improve it?

public static void cat(File named) {
  RandomAccessFile input = null;
  String line = null;
  try {
    input = new RandomAccessFile(named, “r”);
    while ((line = input.readLine()) != null {
      System.out.println(line);
    }
    return;
  } finally {
    if (input != null) {
      input.close();
    }
  }
}

Doesn't `public static void cat(File named) throws IOException` work? — johnchen902, Apr 20 '13 at 08:50
it will give a compilation error because you are not handling the checked exception `IOException` — Arun P Johny, Apr 20 '13 at 08:53
You need to handle it either using `catch` block or throw it back to the caller by changing the method signature as suggested by @johnchen902 — Arun P Johny, Apr 20 '13 at 08:54

score 2 · Answer 1 · answered Apr 20 '13 at 08:54

2

The code has to throw the IOException - try editing your code with eclipse and you would also get a suggestion to throw the Exception.

Also Java 1.7 has the new concept of "try-with-resources" - see the try statement below. The resource used in try (...) is closed automatically.

public static void cat(File named) throws IOException
{
    try (RandomAccessFile input = new RandomAccessFile(named, "r"))
    {
        String line = null;
        while ((line = input.readLine()) != null)
        {
            System.out.println(line);
        }
    }
}

answered Apr 20 '13 at 08:54

michael_s

2,515
18
24

3

you do not need a try-catch-finally block if you force the method to throw any exception – shiladitya Apr 20 '13 at 08:59
2

oh? - the "try-with-resource" is used for closing the file - no need to down-vote in case you don't know what you're talking about, right? – michael_s Apr 20 '13 at 09:00

Maroun · Accepted Answer · 2013-04-20T09:00:58.707

What kind of problem may occur for this code?

public RandomAccessFile throws FileNotFoundException.
public final String readLine() throws IOException.
public void close() throws IOException.

Since public class FileNotFoundException extends IOException

You can change your method to:

public static void cat(File named) throws IOException

And now you don't need a try-catch blocks.

And the caller should catch the exception thrown by the method.

But why don't you want to catch the exceptions?

score 0 · Answer 3 · answered Apr 20 '13 at 08:56

add the throws declaration in your method , and then caller of this method should have try catch block for this exception .

public static void cat(File named) throws IOException {
      RandomAccessFile input = null;
      String line = null;
      try {
        input = new RandomAccessFile(named, "r");
        while ((line = input.readLine()) != null ){
          System.out.println(line);
        }
        return;
      } finally {
        if (input != null) {
          input.close();
        }
      }
    }
  //caller 
   try{
     Class.cat(new File("abc.txt"));
    }catch(IOException e)
    {
      //
    }

you do not need a try-catch-finally block if you force the method to throw any exception — shiladitya, Apr 20 '13 at 08:59
try with finally to close the resources , catch block is not there. — Ahsan, Apr 20 '13 at 09:48

Can I miss the catch clause to throw exception to its caller?

3 Answers3