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Groups > comp.lang.java.programmer > #29345

Re: Java blunders

From Roedy Green <see_website@mindprod.com.invalid>
Newsgroups comp.lang.java.programmer
Subject Re: Java blunders
Date 2014-07-26 10:53 -0700
Organization Canadian Mind Products
Message-ID <jfq7t99ml3keeofs0kpvk7kv1c5obiteb7@4ax.com> (permalink)
References <jvbts91r2f9onj1e3dbr5lvqp70hmofkum@4ax.com> <b501t91t79vgntop0kl5459ffaq5r6d2l1@4ax.com>

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On Wed, 23 Jul 2014 20:48:25 -0700, Gene Wirchenko <genew@telus.net>
wrote, quoted or indirectly quoted someone who said :

>  3) a well-performing String type.  String has + and += which suit
>what I like to do, but Strings have a performance penalty.


I have three ideas to improve the efficiency of the way String is
implemented:

When a String is created the JVM copies a char[] into a new char[]
attached to the String. It does not simply put a reference to the
char[] into the String because it is worried somebody might
subsequently change the contents of the char[], thus violating the
immutability contract of String. However, almost never does anyone
change a char[] after feeding it to new String. I think the JVM could
take advantage of that. If it knew for sure no one would change it, it
could safely and rapidly just insert a reference. If it was not sure,
it might just insert the reference anyway and put a lock on it, so
that if anyone ever did try to change it, they would be blocked, the
char[] could be copied, and the write completed to the old char[] and
the String could attach itself to the new copy of the char[].

Interned Strings are dangerous. Both interned and non-Interned Strings
have the same type — namely String. You must manually manage the
intern method to control precisely when the interning is done.  You
must use either == or equals.  If you get it wrong, there are no error
messages, just puzzling results. So I suggest using an Interned
separate type for interned Strings.  You would use == both for
interned and non-interned String compare. They are automatically
interned as appropriate (managed in much the way hashCode is).

There are two kinds of String:
sequential: Strings you either treat as an atomic whole, treat char by
char starting from the beginning.
random: Strings you operate on randomly with charAt or substring.
I suggest sequential Strings be stored internally in UTF-8 to conserve
RAM. I suggest random Strings be stored in 32-bit UTF-32 code points
for ease of processing. The compiler would have to guess which type a
given String should be. It might have to change its mind and convert
the String part way through run time. It might even store some Strings
in both forms. The readers and writers when using UTF-8 should be able
to take advantage of the fact no translation is necessary. You could
have two separate types for sequential  (UString) and random (String)
in the Java language, but would be to onerous for programmers.
-- 
Roedy Green Canadian Mind Products http://mindprod.com
The art of strongly-typed language design is largely arranging 
that errors are automatically detected as soon as possible
in the compose, compile, run cycle.

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Thread

Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-22 11:41 -0700
  Re: Java blunders Daniele Futtorovic <da.futt.news@laposte.net> - 2014-07-22 21:12 +0200
    Re: Java blunders Arne Vajhøj <arne@vajhoej.dk> - 2014-07-22 19:46 -0400
      Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-23 04:14 -0700
  Re: Java blunders Joerg Meier <joergmmeier@arcor.de> - 2014-07-22 23:47 +0200
    Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-23 04:23 -0700
      Re: Java blunders Martin Gregorie <martin@address-in-sig.invalid> - 2014-07-23 12:32 +0000
        Re: Java blunders Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-07-23 08:55 -0400
          Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-23 06:21 -0700
        Re: Java blunders Arne Vajhøj <arne@vajhoej.dk> - 2014-07-23 19:53 -0400
          Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-23 18:49 -0700
      Re: Java blunders Arne Vajhøj <arne@vajhoej.dk> - 2014-07-23 19:52 -0400
  Re: Java blunders Arne Vajhøj <arne@vajhoej.dk> - 2014-07-22 19:44 -0400
    Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-23 04:27 -0700
      Re: Java blunders Arne Vajhøj <arne@vajhoej.dk> - 2014-07-23 19:55 -0400
        Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-23 18:53 -0700
          Re: Java blunders Joerg Meier <joergmmeier@arcor.de> - 2014-07-24 11:24 +0200
            Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-25 06:34 -0700
          Re: Java blunders Arne Vajhøj <arne@vajhoej.dk> - 2014-07-24 19:31 -0400
            Re: Java blunders Gene Wirchenko <genew@telus.net> - 2014-07-25 13:22 -0700
              Re: Java blunders Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-07-25 17:17 -0400
                Re: Java blunders Martin Gregorie <martin@address-in-sig.invalid> - 2014-07-25 23:12 +0000
                Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-26 09:06 -0700
                Re: Java blunders Martin Gregorie <martin@address-in-sig.invalid> - 2014-07-26 20:11 +0000
                Re: Java blunders Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-07-26 17:27 -0400
                Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-27 10:49 -0700
                Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-27 10:10 -0700
                Re: Java blunders Gene Wirchenko <genew@telus.net> - 2014-07-28 13:53 -0700
                Re: Java blunders Stuart <DerTopper@web.de> - 2014-07-30 08:05 +0200
                Re: Java blunders Sebastian <news@seyweiler.dyndns.org> - 2014-07-30 11:12 +0200
                Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-27 10:13 -0700
                Re: Java blunders Martin Gregorie <martin@address-in-sig.invalid> - 2014-07-27 18:28 +0000
                Re: Java blunders Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-07-27 14:46 -0400
                Re: Java blunders Martin Gregorie <martin@address-in-sig.invalid> - 2014-07-27 21:18 +0000
                Re: Java blunders Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-07-27 18:10 -0400
                Re: Java blunders Martin Gregorie <martin@address-in-sig.invalid> - 2014-07-28 01:25 +0000
                Re: Java blunders Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-07-28 08:02 -0400
                Re: Java blunders Mike Amling <mamling@chaff.us> - 2014-07-31 13:26 -0500
                Re: Java blunders Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-07-31 14:48 -0400
                Re: Java blunders "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2014-07-28 13:22 +0100
                Re: Java blunders Martin Gregorie <martin@address-in-sig.invalid> - 2014-07-28 12:52 +0000
                Re: Java blunders Joerg Meier <joergmmeier@arcor.de> - 2014-07-28 23:38 +0200
                Re: Java blunders Martin Gregorie <martin@address-in-sig.invalid> - 2014-07-28 23:17 +0000
                Re: Java blunders Silvio <silvio@internet.com> - 2014-07-29 13:34 +0200
                Re: Java blunders Martin Gregorie <martin@address-in-sig.invalid> - 2014-07-29 12:45 +0000
                Re: Java blunders Silvio <silvio@internet.com> - 2014-07-29 17:10 +0200
                Re: Java blunders Martin Gregorie <martin@address-in-sig.invalid> - 2014-07-29 16:29 +0000
                Re: Java blunders lipska the kat <lipskathekat@example.com> - 2014-07-29 20:15 +0100
                Re: Java blunders Martin Gregorie <martin@address-in-sig.invalid> - 2014-07-29 22:02 +0000
                Re: Java blunders Silvio <silvio@internet.com> - 2014-07-29 22:43 +0200
                Re: Java blunders Martin Gregorie <martin@address-in-sig.invalid> - 2014-07-29 22:10 +0000
                Re: Java blunders Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2014-07-27 19:18 -0500
                Re: Java blunders Gene Wirchenko <genew@telus.net> - 2014-07-28 13:54 -0700
                Re: Java blunders Arne Vajhøj <arne@vajhoej.dk> - 2014-07-31 23:07 -0400
                Re: Java blunders James Hostick <james.hostick@gmail.com> - 2014-08-01 22:10 -0700
            Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-26 08:31 -0700
              Re: Java blunders Martin Gregorie <martin@address-in-sig.invalid> - 2014-07-26 21:04 +0000
                Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-27 10:51 -0700
                Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-28 08:50 -0700
                Re: Java blunders Joerg Meier <joergmmeier@arcor.de> - 2014-07-28 23:42 +0200
              Re: Java blunders Arne Vajhøj <arne@vajhoej.dk> - 2014-07-31 23:04 -0400
          Re: Java blunders Josip Almasi <joe@vrspace.org> - 2014-07-28 22:23 +0200
            Re: Java blunders Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-07-28 16:39 -0400
              Re: Java blunders Josip Almasi <joe@vrspace.org> - 2014-07-29 00:11 +0200
              Re: Java blunders Jukka Lahtinen <jtfjdehf@hotmail.com.invalid> - 2014-07-30 12:07 +0300
                Re: Java blunders Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-07-30 08:05 -0400
    Re: Java blunders Wanja Gayk <brixomatic@yahoo.com> - 2014-07-25 01:34 +0200
      Re: Java blunders Arne Vajhøj <arne@vajhoej.dk> - 2014-07-24 19:43 -0400
  Re: Java blunders Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2014-07-22 21:02 -0500
    Re: Java blunders Leif Roar Moldskred <leifm@huldreskog.lan> - 2014-07-23 02:01 -0500
      Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-23 18:58 -0700
      Re: Java blunders thinbluernime <thinbluernime3@gmail.com> - 2014-07-25 03:55 +0000
        Re: Java blunders Leif Roar Moldskred <leifm@huldreskog.lan> - 2014-07-25 00:32 -0500
          Re: Java blunders thinbluernime <thinbluernime3@gmail.com> - 2014-07-26 07:28 +0000
            Re: Java blunders "Gavino" <invalid@invalid.invalid> - 2014-07-26 19:43 +0200
        Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-25 06:36 -0700
          Re: Java blunders "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2014-07-25 15:47 +0100
            Re: Java blunders David Postill <david.postill@gmail.com> - 2014-07-25 18:29 +0200
            Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-26 09:27 -0700
        Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-25 06:37 -0700
    Re: Java blunders Joerg Meier <joergmmeier@arcor.de> - 2014-07-23 13:17 +0200
      Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-23 06:27 -0700
    Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-23 04:44 -0700
      Re: Java blunders Silvio <silvio@internet.com> - 2014-07-23 16:23 +0200
        Re: Java blunders Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-07-23 12:02 -0400
          Re: Java blunders Silvio <silvio@internet.com> - 2014-07-24 11:37 +0200
            Re: Java blunders Josip Almasi <joe@vrspace.org> - 2014-07-28 22:37 +0200
        Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-23 09:33 -0700
          Re: Java blunders thinbluernime <thinbluernime3@gmail.com> - 2014-07-25 03:57 +0000
        Re: Java blunders Arne Vajhøj <arne@vajhoej.dk> - 2014-07-23 21:38 -0400
          Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-23 18:59 -0700
            Re: Java blunders Martin Gregorie <martin@address-in-sig.invalid> - 2014-07-24 07:33 +0000
          Re: Java blunders Silvio <silvio@internet.com> - 2014-07-24 11:47 +0200
            Re: Java blunders Arne Vajhøj <arne@vajhoej.dk> - 2014-07-24 19:34 -0400
              Re: Java blunders Silvio <silvio@internet.com> - 2014-07-25 08:48 +0200
                Re: Java blunders Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-07-25 08:07 -0400
                Re: Java blunders "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2014-07-25 13:54 +0100
                Re: Java blunders Arne Vajhøj <arne@vajhoej.dk> - 2014-07-31 22:53 -0400
            Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-25 07:04 -0700
        Re: Java blunders Josip Almasi <joe@vrspace.org> - 2014-07-28 22:01 +0200
      Re: Java blunders Josip Almasi <joe@vrspace.org> - 2014-07-28 21:56 +0200
    Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-23 06:28 -0700
      Re: Java blunders Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2014-07-23 08:33 -0500
    Re: Java blunders Arne Vajhøj <arne@vajhoej.dk> - 2014-07-23 21:34 -0400
      Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-23 19:06 -0700
      Re: Java blunders Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2014-07-23 22:11 -0500
        Re: Java blunders Martin Gregorie <martin@address-in-sig.invalid> - 2014-07-24 07:36 +0000
          Re: Java blunders Arne Vajhøj <arne@vajhoej.dk> - 2014-07-24 19:39 -0400
            Re: Java blunders "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2014-07-25 13:40 +0100
        Re: Java blunders Arne Vajhøj <arne@vajhoej.dk> - 2014-07-24 19:38 -0400
          Re: Java blunders Gene Wirchenko <genew@telus.net> - 2014-07-25 13:30 -0700
  Re: Java blunders taqmcg@gmail.com - 2014-07-23 11:26 -0700
    Re: Java blunders Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-07-23 15:14 -0400
      Re: Java blunders thinbluernime <thinbluernime3@gmail.com> - 2014-07-25 04:07 +0000
        Re: Java blunders Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-07-25 08:35 -0400
          Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-26 09:41 -0700
        Re: Java blunders Wanja Gayk <brixomatic@yahoo.com> - 2014-08-03 16:41 +0200
          Re: Java blunders Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-08-03 11:31 -0400
    Re: Java blunders Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2014-07-23 22:41 -0500
      Re: Java blunders taqmcg@gmail.com - 2014-07-24 10:09 -0700
        Re: Java blunders "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2014-07-25 13:22 +0100
        Re: Java blunders Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2014-07-25 20:34 -0500
          Re: Java blunders "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2014-07-28 13:33 +0100
            Re: Java blunders Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2014-07-28 08:35 -0500
        Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-26 09:44 -0700
          Re: Java blunders Martin Gregorie <martin@address-in-sig.invalid> - 2014-07-26 23:36 +0000
  Re: Java blunders Gene Wirchenko <genew@telus.net> - 2014-07-23 20:48 -0700
    Re: Java blunders Silvio <silvio@internet.com> - 2014-07-24 11:56 +0200
      Re: Java blunders Silvio <silvio@internet.com> - 2014-07-24 16:07 +0200
        Re: Java blunders Gene Wirchenko <genew@telus.net> - 2014-07-25 13:38 -0700
          Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-26 10:02 -0700
    Re: Java blunders Arne Vajhøj <arne@vajhoej.dk> - 2014-07-24 19:29 -0400
      Re: Java blunders Gene Wirchenko <genew@telus.net> - 2014-07-25 13:45 -0700
    Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-26 10:53 -0700
  Re: Java blunders Wanja Gayk <brixomatic@yahoo.com> - 2014-07-25 01:28 +0200
  Re: Java blunders "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2014-07-25 14:16 +0100
  Re: Java blunders Joerg Meier <joergmmeier@arcor.de> - 2014-07-25 17:39 +0200
  Re: Java blunders Roedy Green <see_website@mindprod.com.invalid> - 2014-07-26 16:21 -0700
  Re: Java blunders Josip Almasi <joe@vrspace.org> - 2014-07-28 23:59 +0200
    Re: Java blunders Josip Almasi <joe@vrspace.org> - 2014-07-29 00:41 +0200
      Re: Java blunders Josip Almasi <joe@vrspace.org> - 2014-07-29 01:54 +0200
    Re: Java blunders Arne Vajhøj <arne@vajhoej.dk> - 2014-07-31 22:38 -0400
    Re: Java blunders Arne Vajhøj <arne@vajhoej.dk> - 2014-07-31 22:39 -0400
  Re: Java blunders w.tom.adams@gmail.com - 2014-07-30 07:57 -0700
    Re: Java blunders Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2014-07-30 10:22 -0500

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