Should i catch all the exception which are thrown by a method?

Question

try{
   output.format(\"%d %s %s %.2f%n\", input.nextInt(),
        input.next(),input.next(),input.nextDouble());
} catch(FormatterClosedException formatterClosedExcept         


        

Answer 1

In Java Exceptions are used for marking unexpected situations. For example parsing non-numeric String to a number (NumberFormatException) or calling a method on a null reference (NullPointerException). You can catch them in many ways.

try{
    //some code
} catch (FormatterClosedException e1) {
    e.printStackTrace()     //very important - handles the Exception but prints the information!
} catch (NoSuchElementException e2) {
    e.printStackTrace();
}

or using the fact, that they all extend Exception:

try {
    //somecode
} catch (Exception e) {
    e.printStackTrace;
};

or since Java 7:

try {
    //somecode
} catch (FormatterClosedException | NoSuchElementExceptione) {
    e.printStackTrace;
};

You have to catch all checked exceptions. It's due to the language grammar. On the other hand, there are unchecked exceptions which doesn't necessarily need to be caught.

IllegalArgumentException is unchecked exception and therefor doesn't need to be caught. NoSuchInputException can be thrown by input.next(). That's why it's declared to be caught.

So:

1. you're dealing with 3 different Exceptions.
2. They all are unchecked so don't have to be caught.
3. input.next() can throw NoSuchElementException
4. format can throw FormatterClosedException

Answer 2

Document: java.util.NoSuchElementException is a RuntimeException which can be thrown by different classes in Java like Iterator, Enumerator, Scanner or StringTokenizer.

In your case it is Scanner. Its not from format method.

It's just to be in the safer side(if next input is not given then throw this exception).

Sample code which shows the demo

public class NoSuchElementExceptionDemo{
    public static void main(String args[]) {
        Hashtable sampleMap = new Hashtable();
        Enumeration enumeration = sampleMap.elements();
        enumeration.nextElement();  //java.util.NoSuchElementExcepiton here because enumeration is empty
    }
}

Output:
Exception in thread "main" java.util.NoSuchElementException: Hashtable Enumerator
        at java.util.Hashtable$EmptyEnumerator.nextElement(Hashtable.java:1084)
        at test.ExceptionTest.main(NoSuchElementExceptionDemo.java:23)

Answer 3

add another catch with Exception class. That is the parent class.

catch(Exception e){
//your message or
     System.out.print(e.getMessage());
}

You can add catch for every exception that your code throws and in the end add this catch with this Exception parent class. If your exception is not caught by any of the catch then this will caught your exception.

It will catch all exceptions that is raised by your program.