Java Programming - Exceptions - Discussion

class X
{
public static void main(String [] args)
{
try
{
badMethod();
System.out.print("A");
}
catch (Exception ex)
{
System.out.print("B");
}
finally
{
System.out.print("C");
}
System.out.print("D");
}
public static void badMethod()
{
//throw new Error(); /* Line 22 */
}
}

Now why output ACD plz explain catch not excute?

Here is an explanation why 'C' is the answer.

1. The class is instantiated.
2. Going to try() block.
3. badMethod() is called.
4. badMethod() throwing an Error.
5. Going back to try() block, it doesn't have anything to handle the Error because Exceptions and Errors two separate things.
6. The catch (Exception ex) only catches exceptions, not errors.
7. Finally() block is executed...ALWAYS!!!(No matter what happened in the try() & catch() blocks).
8. C is printed then the error message get printed.

/* Function to check if x is power of 2*/
bool isPowerOfTwo(int n)
{
  if(n == 0)
    return 0;
  while(n != 1)
  {
    n = n/2;
    if(n%2 != 0 && n != 1)
      return 0;
  }
  return 1;
}

Call the above function from your code. That's all.

@Sahil

You made line 22 as comment. So the fn throw new Error(); is not bother.

No error has occurred (exception) and further the return type is void so catch does not work at all.

So it execute the finally block and further on.

I had compiled it & it shows as below.

CException in thread "main" java.lang.Error
at X.badMethod(X.java:22)
at X.main(X.java:7)

I had noted as if nothing got printed like"c".
Can anyone explain?

Hello @Sangeethar and @Murali.

The "C" is actually printed but it is concatenated with the word Exception as "CException in thread. Java. Lang. Error". This is because the coder used "print() " instead of "println() ".

@Bindu.

Before the compiler reaches the print statement for 'A', badMethod () is called where an error is created and now the compiler will go and check for any error handling methods, so A won't be printed.

If in this code I want to execute catch statement then what changes I have to make?

And what is the meaning by this that Exception is not a super class of error();

Exception is not a super class of error means error class is not extends Exception. That is reason catch block is not executing directly it executes finally block.

I want to write a program if I enter a number it will check whether the the number is the power of two or not I want a complete program please reply soon.