Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.java.programmer > #30292

Re: Java 7 vs 8 speed issues on Win7?

Show key headers only | View raw

Hi,

Eric Sosman schrieb:
>      I, too, wonder what he meant by "changed semantics," since as far
> as I know the contract of String#substring(int,int) has not changed
> since Java 1.0, and perhaps earlier.  The underlying implementations
> have changed, I believe, but that's not what I'd call a "semantic"
> difference.

I don't think a method signature (=contract) alone
defines any semantics. BTW: There was a thread here on 
comp.lang.java.programmer about the changed semantics
of substring(int,int). One can lookup the results there.

HashMap was mentioned already in this thread, but I think
it was also discussed here before. String deduplication is
also already mentioned, but this has to be activated by 
-XX:+UseStringDeduplication I guess. Maybe there is
somewhere a list of all the differences.

I know about some existing applications that had problem
cz of the substring(int,int) change, in particular a
parser that relied on the semantics that substring(int,int)
does share the original char[] array. But this semantics
has been replaced by another semantics now, where a range
of the char[] array is copied.

Bye

That the semantic has changed can also be seen by the
fields that the String class now features (JDK 8):

     private final char value[];
     private int hash;

(See for example:
http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/8-b132/java/lang/String.java 
)

The field offset and count is now gone. The old
String class featured the following fields (for example
JDK 6):

     private final char value[];
     private int hash;
     private final int offset;
     private final int count;

(See for example:
http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/lang/String.java 
)

So the internal contract has massively changed.

Back to comp.lang.java.programmer | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Java 7 vs 8 speed issues on Win7? Knute Johnson <eternal@knutejohnson.com> - 2014-10-22 10:18 -0700
  Re: Java 7 vs 8 speed issues on Win7? Silvio <silvio@internet.com> - 2014-10-24 11:10 +0200
  Re: Java 7 vs 8 speed issues on Win7? Roedy Green <see_website@mindprod.com.invalid> - 2014-11-05 04:36 -0800
    Re: Java 7 vs 8 speed issues on Win7? Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2014-11-05 08:23 -0800
      Re: Java 7 vs 8 speed issues on Win7? Jan Burse <janburse@fastmail.fm> - 2014-11-05 20:47 +0100
        Re: Java 7 vs 8 speed issues on Win7? Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2014-11-05 17:32 -0800
          Re: Java 7 vs 8 speed issues on Win7? Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-11-05 21:37 -0500
            Re: Java 7 vs 8 speed issues on Win7? Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2014-11-05 20:00 -0800
              Re: Java 7 vs 8 speed issues on Win7? Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-11-05 23:32 -0500
                Re: Java 7 vs 8 speed issues on Win7? Robert Klemme <shortcutter@googlemail.com> - 2014-11-06 08:48 +0100
                Re: Java 7 vs 8 speed issues on Win7? Jan Burse <janburse@fastmail.fm> - 2014-11-06 15:09 +0100
                Re: Java 7 vs 8 speed issues on Win7? Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-11-06 09:50 -0500
                Re: Java 7 vs 8 speed issues on Win7? Jan Burse <janburse@fastmail.fm> - 2014-11-06 18:21 +0100
                Re: Java 7 vs 8 speed issues on Win7? Jan Burse <janburse@fastmail.fm> - 2014-11-06 18:34 +0100
                Re: Java 7 vs 8 speed issues on Win7? Jan Burse <janburse@fastmail.fm> - 2014-11-06 23:03 +0100
                Re: Java 7 vs 8 speed issues on Win7? Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-11-06 17:21 -0500
                Re: Java 7 vs 8 speed issues on Win7? Jan Burse <janburse@fastmail.fm> - 2014-11-07 00:07 +0100
                Re: Java 7 vs 8 speed issues on Win7? "Bob(but not" THAŢ "Bob)" <nobody@nowhere.net> - 2014-11-07 08:48 +0000
                Re: Java 7 vs 8 speed issues on Win7? Jan Burse <janburse@fastmail.fm> - 2014-11-08 11:28 +0100
        Re: Java 7 vs 8 speed issues on Win7? Roedy Green <see_website@mindprod.com.invalid> - 2014-11-20 03:12 -0800
          Re: Java 7 vs 8 speed issues on Win7? Silvio <silvio@internet.com> - 2014-11-20 13:24 +0100
            Re: Java 7 vs 8 speed issues on Win7? Robert Klemme <shortcutter@googlemail.com> - 2014-11-20 19:06 +0100
              Re: Java 7 vs 8 speed issues on Win7? Silvio <silvio@internet.com> - 2014-11-20 22:54 +0100
                Re: Java 7 vs 8 speed issues on Win7? Brixomatic <brixomatic@yahoo.com> - 2014-11-22 08:54 +0100
                Re: Java 7 vs 8 speed issues on Win7? Brixomatic <brixomatic@yahoo.com> - 2014-11-22 09:19 +0100
    Re: Java 7 vs 8 speed issues on Win7? Fredrik Jonson <fredrik@jonson.org> - 2014-11-29 07:44 +0000

csiph-web