What is the exception I should be catching on the dotted line?

Question

I have a problem at school. I'm new to programing and I need some help. Please complete the dotted line:

import java.net.*; 
import java.io.*
public class Test{
public static void main (String arg[]} 
    int x=0;
    try { 
        ServerSocket s=new ServerSocket ( k ); 
        s.close();
    } 
    catch (..........................) {x++;}
    catch(IOException e) {}
    }
    System.out.println( "Total "+ x); }
}

Answer 1

Look up in the documentation what exceptions the constructor of ServerSocket can throw and what exception the close function of ServerSocket can throw. One of them is probably IOException, just look up what else.

Answer 2

The answer can be found at the JavaDoc for ServerSocket constructor that you use.

Answer 3

You need to catch (or declare that your method throws) every Checked Exception that is declared by the code that you are calling. These are documented in the JavaDoc and on the method signature. Unchecked exceptions, like IllegalArguementException, do not need to be caught.

Answer 4

If you use an IDE, such as Eclipse, you can easily fix those problems and many others, as the IDE will point out exactly what Exceptions need to be caught, saving you from a trip to the Javadoc page which, by the way, is easily accessed directly from the IDE.

@akf: That's not the opinion of the instructors of some major CS schools. For example, the "Introduction to Computer Science | Programming Methodology" course of Stanford uses a modified version of Eclipse. I think it's a much better way to learn a language, avoiding those situations where you are fixing a problem, compile, and then fix the new problem. This can be frustrating to newcomers. An IDE is just a tool to aid programming, it doesn't cause dependence, and it certainly won't stop you from coding without it.

I do agree, however, that it's important to know the basics, as far as using java or javac is concerned, just in case you ever find yourself with a terminal in front of you.

Answer 5

A hint: if you use a modern IDE, it'll tell you. For example, just write without the try and catch blocks

import java.net.*; import java.io.*
public class Test{
public static void main (String arg[]} 
    int x=0;
    ServerSocket s=new ServerSocket ( k ); 
    s.close();
    System.out.println( "Total "+ x); }
}

The IDE will underline the code and give you a suggestion, click on it and it'll insert the appropriate Exceptions automatically.

Answer 6

To make the code compile, the line should read:

catch (StackOverflowError exc) {x++;}

Answer 7

As you mention in your comment on Henri, you have to choose between either SecurityException or IllegalArgumentException.

The significance here lies in the variable x. What is x supposed to count? My guess would be the former, but there should be a hint in your assignment.

(BTW: I only see a mention of SecurityException besides IOException in the documentation)