not able to understand output of the program related to exception handling?

[gurpeet singh]

please consider following program

import java.io.IOException;

public class Dump39 {

    public static void main(String... args)  {

        Dump39 d = new Dump39();
        d.go();

    }

    void go()  {
        try {

            System.out.println("m in try block");
            throw new ArrayIndexOutOfBoundsException();

        } catch (ArrayIndexOutOfBoundsException e) {
            System.out.println("array index out of bounds");

            throw new ClassCastException();

        } catch (ClassCastException ce) {
            System.out.println("class cast exception");
        } finally {
            System.out.println("i am always executed");

        }
    }
}

when i run this program it gives the output as :

m in try block
Exception in thread "main" java.lang.ClassCastException // why does this prints before printing next line i.e. before array index out of bounds
array index out of bounds
i am always executed
at Dump39.go(Dump39.java:30)
at Dump39.main(Dump39.java:17)
Java Result: 1


when ArrayIndexOutOfBoundsException occurs the control goes to first catch block so it must first print "array index out of bounds" and then should throw ClassCastException. but it happens opposite. please help ?

[dharmendra gahlot]

Program output is as below with Java 5 and Java 6.

m in try block
array index out of bounds
i am always executed
Exception in thread "main" java.lang.ClassCastException
at Dump39.go(Dump39.java:21)
at Dump39.main(Dump39.java:8)

[John Jai]

Are you using an IDE like Eclipse? I can see the difference when running in Eclipse and cmd prompt.

Eclipse output:

Exception in thread "main" java.lang.ClassCastException
	at ranch.Dump39.go(Dump39.java:22)
	at ranch.Dump39.main(Dump39.java:9)
m in try block
array index out of bounds
i am always executed

cmd prompt output:

m in try block
array index out of bounds
i am always executed
Exception in thread "main" java.lang.ClassCastException
        at Dump39.go(Dump39.java:21)
        at Dump39.main(Dump39.java:8)

I have experienced this previously in Eclipse.

[Sumit Patil]

Hope this helps.

[Joanne Neal]

Your System.out.println calls are written to standard output.
The Exception in thread "main" java.lang.ClassCastException message is written to standard error.
Because you are writing to different output streams and the i/o is asynchronous there is no guarantee of the order in which the messages will be written.
If you want to guarantee the order, change the System.out.println calls to System.err.println calls

[dharmendra gahlot]

Thanks Joanne Neal..

[John Jai]

Thanks Joanne.