Groups > comp.lang.java.programmer > #5324

Re: Class.forName().newInstance() vs new

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From	lewbloch <lewbloch@gmail.com>
Newsgroups	comp.lang.java.programmer
Subject	Re: Class.forName().newInstance() vs new
Date	Wed, 15 Jun 2011 06:58:56 -0700 (PDT)
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On Jun 12, 7:37 am, Martin Gregorie <mar...@address-in-sig.invalid>
wrote:
> On Sun, 12 Jun 2011 07:10:07 -0700, Patricia Shanahan wrote:
> > Is there really any program that instantiates so many database managers
> > that the difference between newInstance and constructor, and the
> > pipeline reloads related to conditional branches, become measurable?
>
> Is there actually that much difference? It strikes me that both 'new' and
> Class.forName() are doing essentially the same, namely searching the
> class path for the required class, loading it into the JVM and
> instantiating an object from it. I also wonder if 'new' might not be
> implemented as a wrapper for Class.forName(). It certainly could be done
> that way: both return a class object if they are successful and throw an
> exception if the class can't be found.

'new' is not a wrapper for 'Class.forName()' because while 'forName()'
does return a class object, 'new' does not unless the class
instantiated actually is 'Class'.  Since the constructors for 'Class'
are not exposed, that's unlikely.

'newInstance()' is different from 'new' also.  It's invoked
reflectively, i.e., via runtime mechanisms, not via a compiled
constructor invocation as via 'new', and throws different exceptions
from the corresponding constructor.  It's also semantically limited to
no-arg constructors.

'newInstance()' appears in a reflective context which is perforce
going to be slower than compiled-in decisions.  Such a context will
properly appear only when performance is not the overarching concern,
nor readability.

--
Lew

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Thread

Class.forName().newInstance() vs new Abu Yahya <abu_yahya@invalid.com> - 2011-06-11 22:43 +0530
  Re: Class.forName().newInstance() vs new David Lamb <dalamb@cs.queensu.ca> - 2011-06-11 13:46 -0400
  Re: Class.forName().newInstance() vs new Robert Klemme <shortcutter@googlemail.com> - 2011-06-11 19:49 +0200
    Re: Class.forName().newInstance() vs new Patricia Shanahan <pats@acm.org> - 2011-06-11 11:04 -0700
      Re: Class.forName().newInstance() vs new Abu Yahya <abu_yahya@invalid.com> - 2011-06-11 23:52 +0530
      Re: Class.forName().newInstance() vs new Robert Klemme <shortcutter@googlemail.com> - 2011-06-12 14:05 +0200
        Re: Class.forName().newInstance() vs new Patricia Shanahan <pats@acm.org> - 2011-06-12 07:10 -0700
          Re: Class.forName().newInstance() vs new Martin Gregorie <martin@address-in-sig.invalid> - 2011-06-12 14:37 +0000
            Re: Class.forName().newInstance() vs new Robert Klemme <shortcutter@googlemail.com> - 2011-06-12 18:17 +0200
              Re: Class.forName().newInstance() vs new Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-06-12 15:25 -0400
            Re: Class.forName().newInstance() vs new lewbloch <lewbloch@gmail.com> - 2011-06-15 06:58 -0700
              Re: Class.forName().newInstance() vs new Nigel Wade <nmw-news@ion.le.ac.uk> - 2011-06-16 10:16 +0100
          Re: Class.forName().newInstance() vs new Robert Klemme <shortcutter@googlemail.com> - 2011-06-12 18:10 +0200
    Re: Class.forName().newInstance() vs new Abu Yahya <abu_yahya@invalid.com> - 2011-06-11 23:53 +0530
      Re: Class.forName().newInstance() vs new "John B. Matthews" <nospam@nospam.invalid> - 2011-06-11 15:43 -0400
        Re: Class.forName().newInstance() vs new "John B. Matthews" <nospam@nospam.invalid> - 2011-06-11 15:50 -0400
          Re: Class.forName().newInstance() vs new lewbloch <lewbloch@gmail.com> - 2011-06-15 06:49 -0700
            Re: Class.forName().newInstance() vs new Michael Wojcik <mwojcik@newsguy.com> - 2011-06-16 11:21 -0400
              Re: Class.forName().newInstance() vs new lewbloch <lewbloch@gmail.com> - 2011-06-17 06:45 -0700
                Re: Class.forName().newInstance() vs new Michael Wojcik <mwojcik@newsguy.com> - 2011-06-17 12:29 -0400
                Re: Class.forName().newInstance() vs new Lewis Bloch <lewisbloch@google.com> - 2011-06-17 11:07 -0700
                Re: Class.forName().newInstance() vs new "John B. Matthews" <nospam@nospam.invalid> - 2011-06-18 02:01 -0400
                Re: Class.forName().newInstance() vs new Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-06-18 10:19 -0300
                Re: Class.forName().newInstance() vs new Robert Klemme <shortcutter@googlemail.com> - 2011-06-18 20:16 +0200
                OT language stuff (was Re: Class.forName().newInstance() vs new) blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-06-20 19:19 +0000
                Re: OT language stuff (was Re: Class.forName().newInstance() vs new) Martin Gregorie <martin@address-in-sig.invalid> - 2011-06-20 20:46 +0000
                Re: OT language stuff (was Re: Class.forName().newInstance() vs new) blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-06-21 20:42 +0000
                Re: OT language stuff (was Re: Class.forName().newInstance() vs new) Gene Wirchenko <genew@ocis.net> - 2011-06-21 14:22 -0700
                Re: OT language stuff (was Re: Class.forName().newInstance() vs new) Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-06-20 18:55 -0300
                Re: OT language stuff (was Re: Class.forName().newInstance() vs new) Tom Anderson <twic@urchin.earth.li> - 2011-06-21 23:29 +0100
                Re: OT language stuff (was Re: Class.forName().newInstance() vs new) Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-06-21 20:39 -0300
                Re: OT language stuff (was Re: Class.forName().newInstance() vs new) "John B. Matthews" <nospam@nospam.invalid> - 2011-06-21 23:00 -0400
                Re: OT language stuff (was Re: Class.forName().newInstance() vs new) Tom Anderson <twic@urchin.earth.li> - 2011-06-22 20:02 +0100
                Re: OT language stuff (was Re: Class.forName().newInstance() vs new) blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-06-22 20:03 +0000
                Re: OT language stuff (was Re: Class.forName().newInstance() vs new) Michael Wojcik <mwojcik@newsguy.com> - 2011-06-23 12:04 -0400
                Re: OT language stuff (was Re: Class.forName().newInstance() vs new) Michael Wojcik <mwojcik@newsguy.com> - 2011-06-23 11:58 -0400
                Re: Class.forName().newInstance() vs new Gene Wirchenko <genew@ocis.net> - 2011-06-20 14:01 -0700
                Re: Class.forName().newInstance() vs new Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-06-20 18:53 -0300
                Re: Class.forName().newInstance() vs new Michael Wojcik <mwojcik@newsguy.com> - 2011-06-21 19:53 -0400
                Re: Class.forName().newInstance() vs new blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-06-22 20:01 +0000
                Re: Class.forName().newInstance() vs new Michael Wojcik <mwojcik@newsguy.com> - 2011-06-23 12:16 -0400
                OT language stuff (was Re: Class.forName().newInstance() vs new) blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-06-20 19:18 +0000
                Re: OT language stuff (was Re: Class.forName().newInstance() vs new) Martin Gregorie <martin@address-in-sig.invalid> - 2011-06-20 20:52 +0000
        Re: Class.forName().newInstance() vs new Robert Klemme <shortcutter@googlemail.com> - 2011-06-12 14:14 +0200
  Re: Class.forName().newInstance() vs new Patricia Shanahan <pats@acm.org> - 2011-06-11 11:01 -0700
  Re: Class.forName().newInstance() vs new Roedy Green <see_website@mindprod.com.invalid> - 2011-06-13 06:16 -0700
  Re: Class.forName().newInstance() vs new Ian Shef <invalid@avoiding.spam> - 2011-06-14 20:07 +0000

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