Ques from Abhilash 'ssite

[Chaitali Deshpande]

The following code is for Questions 81 and 82

//Contents of File AnInterface.java
public interface AnInterface
{
public void methodOne() throws Exception;
}

//Contents of File AnInterfaceImpl.java
public class AnInterfaceImpl implements AnInterface
{
public void methodOne()
{
System.out.println("I will never throw an exception");
}
}
Question 81.
Read the code below carefully.
public class ATest
{
public static void main(String args[])
{
AnInterface ai = new AnInterfaceImpl();
ai.methodOne();
}
}
Attempting to compile and run the above code
1) Will cause a compile time error. (Line 5 : Exception must be caught or thrown by main(String))
2) Will cause a compile time error for Class AnInterfaceImpl. The method methodOne() be declared with "throws Exception".
3) Will cause no compile time error and print "I will never throw and Exception the screen".
Will Cause a run time error .
-----------------------------------------------------------------
Question 82.
Read the code below carefully.
public class ATest
{
public static void main(String args[])
{
AnInterfaceImpl ai = new AnInterfaceImpl();
ai.methodOne();
}
}
Attempting to compile and run the above code
1) Will cause a compile time error. (Line 5 : Exception must be caught or thrown by main(String))
2) Will cause a compile time error for Class AnInterfaceImpl. The method methodOne() be declared with "throws Exception".
3) Will cause no compile time error and print "I will never throw and Exception the screen".
Will Cause a run time error .

Ans 81)1
82)3
Can someone please explain me the output.
Thanks in advance.

[greg philpott]

make two seperate posts.
Some of us have to work, How much spare time do you think we have?

[Chaitali Deshpande]

greg
I gave them in single post because both question are related.

[Wong KK]

<code>
public class Test {
public static void main(String args[]) {
Parent obj = new Child();
obj.p();
}
}
class Parent {
}
class Child extends Parent {
void p() {
System.out.println("I am Child");
}
}
</code>
Remember that the above code won't compile??
When compilation, all checking is based on the object reference. Late Binding is only occured at runtime.

[Sivalingam Sivasuthan]

Hi Chaitali Deshpande,
As Wong KK is correct at the compilation time, Compiler doesn't know about the child class object's method(In you case It only aware about the Interface method's Signature which requirs to catch the Exception that throws).
Just Check this code.......... It is also the Simmiller.

class ExcetionalParent{
void method()throws java.io.IOException{
throw new java.io.IOException("IOE");
    }
}
class ExcetionalChild extends ExcetionalParent{
void method()throws java.io.FileNotFoundException{
    }
}
public class Caller{
 public static void main(String[]args){
 
 ExcetionalParent ec= new ExcetionalChild();//Parent Class reference having the Child Object reference
 
 try{
 ec.method();
  }catch(java.io.FileNotFoundException ioe){}
   /*
   Here you have to Catch IOException Compiler will say unreported exception
   java.io.IOException; must be caught or declared to be thrown
   */
     }
}

Hope you will be Clear Now.
-Siva