Compiler error complaining about the catch block where no IOException object can ever

[pradeep singh]

Answer to this below question is a>.But i am unable to understand this why a is the answer that is Compiler error complaining about the catch block where no IOException object can ever be thrown.please explain me why ?

What is the result of the following code?

01: public class AQuestion {
02:
03: public static void main(String args[]) {
04:
05: System.out.println("Before Try");
06:
07: try {
08: }
09: catch(java.io.IOException t) {
10: System.out.println("Inside Catch");
11: }
12:
13: System.out.println("At the End");
14: }
15: }


a> Compiler error complaining about the catch block where no IOException object can ever be thrown.
b> Compiler error - IOException not found. It must be imported in the first line of the code.
c< The lines "Before Try" and "At the end" are printed on the screen

[Deepak Jain]

The answer to the question is B.
When you compile the code

try {
}catch(IOException e) {
}

Since IOException is a checked exception if the class IOException must first be imported , But once you place import java.io.IOException you will get compiler error saying "Try block does not throw IOException and hence you should not have.So after you import the answer to the question is a.
Hope this clears.

[Niara Bhonde]

Hi Deepak,

I tried the following and in both cases the compiler doesn't complain:

1. declaring only Exception instead of the IOEXception:
try{
}catch(Exception t)
{
System.out.println("Inside catch");
}

2.try{
System.in.read();
}catch(java.io.IOException t)
{
System.out.println("Inside catch");
}

So what you mean to say is, because IOException is a checked Exception, we have to have code in the try block that might throw an IOException?

[pradeep singh]

yes i agree with Niara Bhonde but why we have to require a statement which might throw an IOException in try block while catching IOException But this is not the case with other exceptions.
Why the code 1. given below is compile but 2.will show compiler errorcPlease explain me ?

1. declaring only Exception instead of the IOEXception:
try{
}catch(Exception t)
{
System.out.println("Inside catch");
}

2.try{
}catch(java.io.IOException t)
{
System.out.println("Inside catch");
}

[Henry Wong]

1. declaring only Exception instead of the IOEXception:
try{
}catch(Exception t) {
    System.out.println("Inside catch");
}

The reason catching Exception compiles, is because Exception (besides being a superclass of IOException), is also the superclass of RuntimeException. This means that unchecked exceptions may also be caught.

Henry

[pradeep singh]

Thanks to you All VERY VERY MUCH to clear my doubt regarding this catching of checked exception.