Following is a question

[Netty poestel]

Following is a question:-


_______________________Begin snip_____________________________________
If the following code is successfully compiled and run without explicitly enabling assertions, what will happen?
class Language{
public static final int java=1;
public static final int pascal=2;
public static final int csharp=3;

}
public class Mgos {
static int lang=0;
public static void main(String argv[]){
switch(lang){
case Language.java:
System.out.println("java");
break;
case Language.pascal:
System.out.println("pascal");
break;
case Language.csharp:
System.out.println("csharp");
break;
default:
assert false : lang;
}

}

}

1) An unmatched parameter exception will be thrown
2) An assert exception will be thrown
3) The program will run with no output
4) Output of "csharp"
___________end snip_________________________________________

what should be the answer and why ?

Thanks

[marc weber]

This might be a good exercise in preparing for the exam: Have you compiled and run this program -- both with and without assertions enabled? What was your result? Is this different than what you expected? If so, how?

Code with UBB tags...

class Language{
   public static final int java = 1;
   public static final int pascal = 2;
   public static final int csharp = 3;
}
 
public class Mgos{
   static int lang = 0;
   public static void main(String argv[]){
      switch(lang){
         case Language.java: System.out.println("java");
         break;
         case Language.pascal: System.out.println("pascal");
         break;
         case Language.csharp: System.out.println("csharp");
         break;
         default: assert false: lang;
      }
   }
}

[ September 26, 2004: Message edited by: marc weber ]

[Andy Chang]

If assertions are disabled, the program will run with no output.

However, if assertions are enabled, the assert will fail and an AssertionError will be thrown.
An acceptable alternative is:
default:
throw new AssertionError(lang);

[Netty poestel]

Thanks all.
I'm fine about the assert statement.
If I take it out, there is compilation but no output.
This no output was my bother.
Do I understand that static int lang=0;
thus it's value will remain 0 throughout this code piece.

so the 'switch(lang)' is evaluating to switch(0) and since 0 is not the constants '1','2' and '3' thus none of the case gets printed out...right ?

however if I compile with -source 1.4 and the run with -ea, then the assertion error gets thrown...
well it got clear as I wrote this mail....so thanks for those feedbacks..

[marc weber]

Netty,

That's exactly right. (And of course, the default is for assertions to be disabled without -ea.)

It's important to compile and run a couple of these before the exam. Reading all about assertions is one thing, but there's nothing like practice to verify and reinforce your understanding.