asked on

chaining exceptions

Hi,

I was working on below example
http://www.avajava.com/tutorials/lessons/how-do-i-chain-exceptions.html?page=2

I got output as below

***no chaining example:
java.lang.Exception: Two
      at ExceptionTest2.main(ExceptionTest2.java:11)

***chaining example 1:
java.lang.Exception: Four
      at ExceptionTest2.main(ExceptionTest2.java:22)
Caused by: java.lang.Exception: Three
      at ExceptionTest2.main(ExceptionTest2.java:20)
###what was the cause:
java.lang.Exception: Three
      at ExceptionTest2.main(ExceptionTest2.java:20)

***chaining example 2:
java.lang.Exception: java.lang.Exception: Five
      at ExceptionTest2.main(ExceptionTest2.java:35)
Caused by: java.lang.Exception: Five
      at ExceptionTest2.main(ExceptionTest2.java:33)

I have not clearly understood how the chaining happening here and the output

please advise
Any links resources ideas highly appreciated. Thanks in advance

ASKER CERTIFIED SOLUTION

Ken Butters

membership

This solution is only available to members.

To access this solution, you must be a member of Experts Exchange.

Start Free Trial

SOLUTION

Mahesh Bhutkar

membership

This solution is only available to members.

To access this solution, you must be a member of Experts Exchange.

Start Free Trial

gudii9

ASKER

That makes more sense.

I wonder why "One" did not printed.

also what is difference between below lines

     e.printStackTrace(System.out);

                  e.getCause().printStackTrace(System.out);

I see both yielding same out put.
what is the purpose of e.getCause()

Please advise

Ken Butters

System.out.println("***no chaining example:");
		try {
			try {
				throw new Exception("One");
			} catch (Exception e) {
				throw new Exception("Two");
			}
		} catch (Exception e) {
			e.printStackTrace(System.out);
		}

Open in new window

In the code above... "One" does not print, because "One" is a new exeception that is thrown.

Exeception "One" is caught by the following catch.

			} catch (Exception e) {
				throw new Exception("Two");
			}

Open in new window

So now you have to ask... one does this catch do? Does it print anything about "One"... no it does not. It simply throws another new exception called "Two".

Exception "Two" is then caught and printed by the following line:
e.printStackTrace(System.out);

the difference between e.printStackTrace(System.out);
and e.getCause().printStackTrace(System.out);

the getcause only prints the cause of the exception, it doesn't print the whole "stack" of errors.

for example in chaining example 1:

e.printStackTrace(System.out);... printed the following:

java.lang.Exception: Four
      at test.ExceptionTest.main(ExceptionTest.java:22)
Caused by: java.lang.Exception: Three
      at test.ExceptionTest.main(ExceptionTest.java:20)

e.getCause().printStackTrace(System.out);... for the exact same exception printed the following:
java.lang.Exception: Three
      at test.ExceptionTest.main(ExceptionTest.java:20)