java 1.4 assertions question

[Kevin Peterson]

For some reason I can't get asserts to work in this program i am writing, I was just wondering if the code I give after the current code will work instead?


-This uses asserts as you can see...

 public BoardPosition(int a, int b){

assert a >= 0 && a < 8 && b >= 0 && b < 8:
     "Illegal board position being created";

                x = a;
y = b;
}
 

As opposed to this , notice the if statement.....

 public BoardPosition(int a, int b){

if(a >= 0 && a < 8 && b >= 0 && b < 8){
    System.out.println( "Illegal board position being                                            created" ) ;
}
x = a;
y = b;

}
 

-Thanks, Kevin
[ April 12, 2005: Message edited by: Kevin Peterson ]

[Nicholas Cheung]

How did you compile and execute the code? Did you compile and execute it by specifying the "enable assertion" option?

Nick

[David Peterson]

By the way, it's generally not a good idea to use assertions for checking the preconditions of public methods or constructors. You should throw an IllegalArgumentException (run-time exception) instead, so that the public contract is enforced whether assertions are turned on or not.

Use assertions for checking the preconditions of non-public methods, or for checking internal consistency and post-conditions.

[David Peterson]

public BoardPosition(int a, int b){
    if ((a < 0) || (a > 7) || (b < 0) || (b > 7)) {
        throw new IllegalArgumentException("Board position (" + a + ", " + b + ") is out of range");
    }
    x = a;
    y = b;
}

To answer your original question, to run the code with assertions use the -ea (or -enableassertions) switch when you run java.

java -ea MyClass

[Kevin Peterson]

yea I understand but i compiled with with this above my code:

 

   //Compile with: javac -source 1.4 BoardPosition.java
   //{JVMArgs: -ea}   
   //{ThrowsException}   
 
  

and got a compile time error. I was just wondering if there was a simple if statement that I stated above that would work?

-Kevin

[Kevin Peterson]

Actully throwing an IllegalArgumentException() works fine, Thanks David.
-Kevin