Re: [Gzz] fourth PEG cursors--humppake: Changing mouse cursor

[Tuomas Lukka]

On Mon, May 12, 2003 at 04:57:05PM +0300, Asko Soukka wrote:
> Mon, 12 May 2003, Tuomas Lukka kirjoitti:
> > >      * "WAIT_CURSOR" The wait cursor type.
> > >      */
> > 
> > ISSUE: Do we *really* want all arguments to this method have the _CURSOR
> > suffix?
> 
> I would prefer it, since then they'll be similar to constants 
> in awt.Cursor. If that's not a good reason enough, then we may drop the 
> suffix. 

They're similar without the suffix as well, especially if you mention 
that. In awt.Cursor there's a *reason* to have the suffix: they are
data members of the class and it makes sense to separate the namespace.
Here, that doesn't make sense.

> Benja?
> 
> > >   if (cursorName == "CROSSHAIR_CURSOR")
> > >     cursor = new Cursor(Cursor.CROSSHAIR_CURSOR);
> > >   else if (cursorName == "DEFAULT_CURSOR")
> > >     cursor = new Cursor(Cursor.DEFAULT_CURSOR);
> ...
> > >   else throw new IllegalArgumentException("Unknown cursor: 
> > > "+cursorName);
> > >   canvas.setCursor(cursor);
> > >     }
> > Using reflection is also possible.
> 
> Reflection? Please, explain.

In Java, you can get the field of the Cursor class through
Cursor.class.getField(name+"_CURSOR").


> > >     cursorName == "SW_RESIZE_CURSOR" ||
> > >     cursorName == "TEXT_CURSOR" ||
> > >     cursorName == "W_RESIZE_CURSOR" ||
> > >     cursorName == "WAIT_CURSOR")
> > 
> > That code won't work. Can't compare strings using ==.
> 
> Of course :/  -> String.equals().
> 
> Mudyc told that std::strings in C++ can be compared
> using '=='. Is that correct? So, the difference is that
> operators can't be overloaded in Java. 

Yes, that's right.

But to confuse things further, in Java, there *is* a special case where
you *can* compare strings with ==  : if you *know* that both strings
have been interned.

        String a, b;

        if(a == b) {} # true if both point to same instance of string,
                      # which can vary
        
        a = a.intern();
        b = b.intern();
        if(a == b) { }  # true if originally a.equals(b).
                    
This is handy for us, we use interned strings as keys in our RDF swamps.

        Tuomas