Java BufferedReader error with try block

Question

I have this method that is supposed to load a file but it is giving me this error:

NamnMetod.java:175: error: unreported exception FileNotFoundException; must be caught or declared to be thrown
                 BufferedReader inFil = new BufferedReader(new FileReader(fil));
                                                           ^
NamnMetod.java:177: error: unreported exception IOException; must be    caught or declared to be thrown
                 String rad = inFil.readLine();  
                                            ^

This is my code:

   public static void hämtaFrånText() {
    try {
     EventQueue.invokeAndWait(new Runnable() {
     @Override

        public void run() {
              String aktuellMapp = System.getProperty("user.dir");
           JFileChooser fc = new JFileChooser(aktuellMapp);
           int resultat = fc.showOpenDialog(null);

              if (resultat != JFileChooser.APPROVE_OPTION) {
                 JOptionPane.showMessageDialog(null, "Ingen fil valdes!");
                 System.exit(0);
              }
                 String fil = fc.getSelectedFile().getAbsolutePath();
                 String[] namn = new String[3];         
                 String output ="";         
                 BufferedReader inFil = new BufferedReader(new FileReader(fil));                    
                 String rad = inFil.readLine();

                 int antal = 0;

                    while(rad != null){                  
                        namn[antal] = rad;
                        rad = inFil.readLine();
                        antal++;
                    }
                    inFil.close();

       }
    });                     
    }catch(IOException e2) {        
        JOptionPane.showMessageDialog(null,"The file was not found!");
    }           
}

I'm perplexed because i have caught both IOException and FileNotFoundException but I still get this error...

follow a proper naming-convention please. It's hard to understand what you are trying to do. — Uma Kanth
– Uma Kanth, Commented Nov 9, 2015 at 8:32
Try putting the try-catch inside the public void run()-method. — Kevin Cruijssen
– Kevin Cruijssen, Commented Nov 9, 2015 at 8:33
@UmaKanth I think the naming convention is fine; it just happens to be in Swedish. — Andy Turner
– Andy Turner, Commented Nov 9, 2015 at 8:34
It's as @KevinCruijssen said. You are catching IOException in the hämtaFrånText() method; in the run() method, where the statement that throws that exception is, there is no try / catch. — SantiBailors
– SantiBailors, Commented Nov 9, 2015 at 8:37
I put the try-catch inside the public void but i still get an error: NamnMetod.java:157: error: unreported exception InterruptedException; must be caught or declared to be thrown EventQueue.invokeAndWait(new Runnable() — samtob
– samtob, Commented Nov 9, 2015 at 8:52

Andy Turner · Accepted Answer · 2015-11-09 08:39:24Z

2

You are catching them in the code which creates the Runnable, whereas the exceptions need to be caught in Runnable.run().

Move the try/catch inside your run method.

Also, use try-with-resources to ensure that the FileReader is always closed, even if an exception occurs:

try (FileReader fr = new FileReader(fil);
     BufferedReader inFil = new BufferedReader(fr)) {
  // ...

  // No need to close `fr` or `inFil` explicitly.
}

edited Nov 9, 2015 at 8:39

answered Nov 9, 2015 at 8:33

Andy Turner

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Comments

Wolfgang Liebich · Accepted Answer · 2015-11-09 08:36:51Z

0

The try-catch block belongs into the run()-Method of the "Runnable" - this run()-Method must not throw any exception. Submitting the Runnable will not throw exceptions.

answered Nov 9, 2015 at 8:36

Wolfgang Liebich

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Comments

Vinay Prajapati · Accepted Answer · 2015-11-09 08:39:11Z

Below is the solution:

public static void hämtaFrånText() {

        try {
            EventQueue.invokeAndWait(new Runnable() {

                @Override
                public void run() {
                    try {
                        String aktuellMapp = System.getProperty("user.dir");
                        JFileChooser fc = new JFileChooser(aktuellMapp);
                        int resultat = fc.showOpenDialog(null);

                        if (resultat != JFileChooser.APPROVE_OPTION) {
                            JOptionPane.showMessageDialog(null, "Ingen fil valdes!");
                            System.exit(0);
                        }
                        String fil = fc.getSelectedFile().getAbsolutePath();
                        String[] namn = new String[3];
                        String output = "";
                        BufferedReader inFil = new BufferedReader(new FileReader(fil));
                        String rad = inFil.readLine();

                        int antal = 0;

                        while (rad != null) {
                            namn[antal] = rad;
                            rad = inFil.readLine();
                            antal++;
                        }
                        inFil.close();
                    }catch(FileNotFoundException e1) {
                        JOptionPane.showMessageDialog(null,"The file was not found!");
                    }
                    catch(IOException e2) {
                        JOptionPane.showMessageDialog(null, "Failed!");
                    }
                }
            });
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }

    }

Reason : run is a method from Runnable and in eventQueue it has been defined and in method definition there is no place where the exception is handled or added in throw in method declaration statement. Hence the FileNoFoundException and IOException both should be given inside the method and not outside.

Also, InterruptedException checked exception was thrown by EventQueue and I added another try catch to handle that exception.

Hope it helps.

And what exactly does this solution show? Answers which dump a big pile of code are not very helpful unless they actually explain what you have changed.

Imrank · Accepted Answer · 2015-11-09 08:41:27Z

0

You need to move your try catch block inside run method, that should do the trick and also you need to handle InvocationTargetException and InterruptedException thrown by EventQueue.invokeAndWait(Runnable) to compile your class properly.

answered Nov 9, 2015 at 8:41

Imrank

1,0195 silver badges15 bronze badges

Comments

Saif · Accepted Answer · 2015-11-09 08:44:02Z

You have scope problem here.

The try and catch you are using will catch the exception of hämtaFrånText()But not of the method run()

Exception can happen inside the method run not out side.

The try-Cathc you have given will only care about exceptions that happens in its scope as you haven't throws those exception, it's not your hämtaFrånText() method to take care what happen inside run().

If run was your defined method then you could have throw them. But now only option you have is to catch them inside the run() method.

So try

public void run() {
try{
.............
...........

    }catch(FileNotFoundException e1) {
        JOptionPane.showMessageDialog(null,"The file was not found!");
        }
     catch(IOException e2) {
        JOptionPane.showMessageDialog(null, "Failed!");
    }
}

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