Re: verbose sort

From: v_borchert@despammed.com (Volker Borchert)

Eric Sosman wrote:
> To: bob smith
> From: Eric Sosman <esosman@ieee-dot-org.invalid>
>
> On 8/2/2012 11:37 AM, bob smith wrote:
> > I have some code that sorts a list like so:
> >
> > Vector<String> my_list = new Vector<String>();
> >
> >
> > Comparator<String> c = new Comparator<String>() {
> > @Override
> > public int compare(String object1, String object2) {
> > if (object1 == null)
> > return -1;
> > if (object2 == null)
> > return 1;
> > object1 = object1.toLowerCase();
> > object2 = object2.toLowerCase();
> > return object1.compareTo(object2);
> > };
> > };
> >
> > Collections.sort(my_list, c);
> >
> >
> > This seems like a lot of code for such a common operation. Is there a more
> succinct way of doing this?
>
> Consider using compareToIgnoreCase(). Also, think about what
> happens when two null's are compared: You should return zero rather than
> declaring one of them "less than" the other, because otherwise your
comparator
> is inconsistent (you can have A<B, B<C, but C<A).
>
> public int compare(String s1, String s2) {
> if (s1 == null)
> return s2 == null ? 0 : -1;
> return s2 == null ? +1 : s1.compareToIgnoreCase(s2);
> }

I'd do it as a fastpath and GoF Decorator

public final class NullFirstComparator<T> implements Comparator<T> {
@NonNull
private final Comparator<T> delegate;

public NullFirstComparator(@NonNull final Comparator<T> delegate) {
this.delegate = delegate;
}

public int compare(final T t1, final T t2) {
if (t1 == t2) {
return 0;
} else if (t1 == null) {
return -1;
} else if (t2 == null) {
return 1;
} else {
return delegate.compare(t1, t2);
}
}
}

Collections.sort(my_list, new NullFirstComparator<String>(String.CASE_INSENSITI
VE_ORDER));

--

"I'm a doctor, not a mechanic." Dr Leonard McCoy <mccoy@ncc1701.starfleet.fed>
"I'm a mechanic, not a doctor." Volker Borchert <v_borchert@despammed.com>

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Volker Borchert wrote:
> --- BBBS/Li6 v4.10 Dada-1
> * Origin: Prism bbs (1:261/38)
> --- Synchronet 3.16a-Win32 NewsLink 1.98
> Time Warp of the Future BBS - telnet://time.synchro.net:24

Currently it's only an annoying echo. Stop it. Now.

--

"I'm a doctor, not a mechanic." Dr Leonard McCoy <mccoy@ncc1701.starfleet.fed>
"I'm a mechanic, not a doctor." Volker Borchert <v_borchert@despammed.com>