Re: getTypeMap() returns null - bug?

On 2020-05-12 06:10, rob stone wrote:
> On Mon, 2020-05-11 at 02:28 -0400, javadesigner wrote:
>> empty is not the same as null in java. this is a java specific
>> discussion btw.
>> 
> 
> Vraimente.
> 
> java.util.Map map = con.getTypeMap();
> 
> So, the variable "map" is now an empty map object. Highly likely it
> contains hex zeroes. It could contain the string "empty" but that does
> not sound reasonable. Maybe there is no memory address and memory is
> only allocated with the first "put".

That is not how maps work in Java. A map is a collection of keys and 
values (aka a hashtable or dictionary), an empty map has no keys (and 
thus no values).

> System.out.println("map:"+map);
> 
> So, println accesses the memory occupied by the object and assuming it
> contains unprintable hex zeroes, it can either display "null", or
> convert to printable zeroes or ignore it and display nothing.
> 
> What output did you expect from  "System.out.println("map:"+map);"??
> That is the question.

Printing out a map is not what you'd normally do in Java, but if you do, 
an empty map will print (without quotes): '{}', assuming the 
java.util.HashMap implementation or the value of 
java.util.Collections.emptyMap().

Mark