assertion

[prajkta patil]

Given the following,

1.   public class Test2 {
2.     public static int x;
3.     public static int foo(int y) {
4.       return y * 2;
5.     }
6.     public static void main(String [] args) {
7.       int z = 5;
8.       assert z > 0;
9.       assert z > 2: foo(z);
10.      if ( z < 7 )
11.      assert z > 4;
12.      switch (z) {
13.        case 4: System.out.println("4 ");
14.        case 5: System.out.println("5 ");
15.        default: assert z < 10;
16.      }
17.      if ( z < 10 )
18.        assert z > 4: z++;
19.      System.out.println(z);
20.    }
21.  }

which line is an example of an inappropriate use of assertions?

A]Line 8

B]Line 9

C]Line 11

D]Line 15

E]Line 18
answer is E. Assert statements should not cause side effects. Line 18 changes the value of z if the assert statement is false.
but i think line 15 is also wrong bcause value of z is 5 & there is no break keyword in the switch stmt,so it will go to default stmt of switch after case 5.& then it will give error.i think author forgot to use break over there.And one more confusion is that z is not the final variable then how can it used in switch stmt of above programme.

pls correct my confusion ,
thanks in advance..

[Dave Wood]

Hi.

While I agree that the lack of break statement is odd, it doesn't really make the assertion in line 15 incorrect. That assertion doesn't fail in the case you described because z IS less than 10 (which is what's being asserted).

As for the variable not being final: that's not a requirement for use in a switch statement. What you're thinking of is that the values in the CASE statements must be constant values. In this example, those values are 4 and 5, which are constants. If you defined a variable:

int FOO = 5;

...and used it in place of the value 5 in the case statement, it would not compile because FOO is not constant.

Hope that helps.

[Mike Gershman]

Please consider that assert statements are used to detect program bugs. If the lack of break statements causes an assert to fail, the assert is just doing its job.

[prajkta patil]

thanks dave & mike.
now i understood well.

[ankur rathi]

So , What would be the answer of question .
I think the code will run without error but there is no option like none of this .

[ankur rathi]

I didnt get the reason for answer E .
please any body help .

[Ramy M. Kamel]

Rathi,

Take care that the question is asking for inappropriate use of assertions, not illegal use.

I think it's mandatory to distinguishe between Illegal and Inappropriate when looking at assertions questions.

[ankur rathi]

How it is inappropriate ???

I am very much confuse now ?

please help .

[ankur rathi]

Please help .

It is confusing me !!

[Sree Nivas]

There should not be any side effects when you are using assertions. Bcoz assertions can be enabled and disabled, z++ in line no 18 gives one output when assertions are enabled and different output when these are disabled. Hence the answer E is correct. The following url also helps when to use assertions and not to use.

http://java.sun.com/j2se/1.4.2/docs/guide/lang/assert.html

Hope this clarifies your query.

Sreenivas