J2SE 1.4 assertion facility

Question

I'm trying to test drive the new assertion facility in J2SE 1.4 but can't get even a simple example to work:
public class Foo
     public void m1( int value )
          assert 0 <= value;
          System.out.println( "OK" );
     public static void main( String[] args )
          Foo foo = new Foo();
          System.out.print( "foo.m1( 1 ): " );
          foo.m1( 1 );
          System.out.print( "foo.m1( -1 ): " );
          foo.m1( -1 );
Code fails with the following error:
Foo.java:5: Invalid expression statement.
assert 0 <= value;
The compiler fails to recognize the 'assert' keyword - when I change code to:
boolean b = true;
assert b;
the error is:
Foo.java:7: Class assert not found.
assert b;
So, it thinks I'm defining a variable b of type assert rather than recognizing the keyword 'assert'!
I've doing all this in the new J2SE 1.4 - I do have other versions of the JDK on my machine, but am pretty sure I'm compiling against the right one - when I type 'java -version' on command line I get:
java version "1.4.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-b92)
Java HotSpot(TM) Client VM (build 1.4.0-b92, mixed mode)
Anyone any ideas?
Thanks,
Alan

Answer 1

what bs. post-condition type assertions typically
"validate the internal state of the receiver".
pre-condition type assertains are typically used to
validate the state of arguments passed in.
Pre-condition type asserts define the "contract" a
caller must agree to prior to calling. It's very
simple, and very effective.No, you shouldn't use assertions to test pre-conditions. The pre-conditions should always be checked, not just in debug mode. Otherwise, the program could behave differently in debug and release modes, and that would be very undesirable!