Re: null objects don't yell; JAVASWARMGDB

[Joshua Madden]

On Mon, 8 Jan 2001, Paul E Johnson wrote:

> Suppose model swarm loops over agents, telling them what to do.  Suppose
> there is some mistake inside the method the agent is carrying out, so
> that it tries to send a message to a null object.  Java makes no error
> message, but instead it terminates the action for the whole loop right
> at that spot.  

My experience with Java is relatively limited, but if it encounters a
null reference unexpectedly, it should throw a NullPointerException and
exit (unless you catch the exception).

You might try the following experiment to confirm that it is indeed a NPE
that is being thrown that causes your code to terminate: enclose the
suspect code in a try-catch block as follows:

try { // code which appears to terminate due to unexpected null reference}
catch (NullPointerException e) 
{ //print something out which confirms that you caught this exception}

No idea about the JavaSwarmGDB, never used it.

Joshua Madden

address@hidden Per Obscurius...cs.uoregon.edu/~jmadden
    Joshua Madden: Information Scientist, Musician, Philosopher-At-Tall
It's that moment of dawning comprehension that I live for--Bill Watterson
My opinions are too rational and insightful to be those of any organization.



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