From: "Shawn O. Pearce" <spearce@spearce•org>
To: Yann Simon <yann.simon.fr@gmail•com>
Cc: Robin Rosenberg <robin.rosenberg.lists@dewire•com>,
git <git@vger•kernel.org>
Subject: Re: [PATCH JGIT] Method invokes inefficient new String(String) constructor
Date: Thu, 19 Mar 2009 09:01:02 -0700 [thread overview]
Message-ID: <20090319160102.GQ23521@spearce.org> (raw)
In-Reply-To: <49C20D4E.5020203@gmail.com>
Yann Simon <yann.simon.fr@gmail•com> wrote:
> From FindBugs:
> Using the java.lang.String(String) constructor wastes memory because
> the object so constructed will be functionally indistinguishable from
> the String passed as a parameter. Just use the argument String directly.
>
> Signed-off-by: Yann Simon <yann.simon.fr@gmail•com>
> ---
> .../src/org/spearce/jgit/lib/RefDatabase.java | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/org.spearce.jgit/src/org/spearce/jgit/lib/RefDatabase.java b/org.spearce.jgit/src/org/spearce/jgit/lib/RefDatabase.java
> index 87f26bf..49da538 100644
> --- a/org.spearce.jgit/src/org/spearce/jgit/lib/RefDatabase.java
> +++ b/org.spearce.jgit/src/org/spearce/jgit/lib/RefDatabase.java
> @@ -447,7 +447,7 @@ private synchronized void refreshPackedRefs() {
>
> final int sp = p.indexOf(' ');
> final ObjectId id = ObjectId.fromString(p.substring(0, sp));
> - final String name = new String(p.substring(sp + 1));
> + final String name = p.substring(sp + 1);
> last = new Ref(Ref.Storage.PACKED, name, name, id);
> newPackedRefs.put(last.getName(), last);
I had a specific reason for forcing a new String object here.
The line in question, p, is from the packed-refs file and
contains the entire SHA-1 in hex form at the beginning of it.
We've converted that into binary as an ObjectId, it uses 1/4 the
space of the string portion.
The Ref object, its ObjectId, and its name string, are going to be
cached in a Map, probably long-term. We're better off shedding the
80 bytes of memory used to hold the hex SHA-1 then risk substring()
deciding its "faster" to reuse the char[] then to make a copy of it.
--
Shawn.
next prev parent reply other threads:[~2009-03-19 16:03 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-19 9:15 [PATCH JGIT] Method invokes inefficient new String(String) constructor Yann Simon
2009-03-19 16:01 ` Shawn O. Pearce [this message]
2009-03-19 16:44 ` Yann Simon
2009-07-09 8:47 ` Yann Simon
2009-07-10 15:34 ` [PATCH] FindBugs: don't use new String(String) in RefDatabase Shawn O. Pearce
2009-07-13 8:07 ` Yann Simon
2009-07-13 14:53 ` [JGIT PATCH v2] " Shawn O. Pearce
2009-07-21 14:50 ` Robin Rosenberg
2009-07-21 15:03 ` Shawn O. Pearce
2009-07-21 19:47 ` Robin Rosenberg
-- strict thread matches above, loose matches on Subject: below --
2009-04-27 23:02 [PATCH JGIT] Computation of average could overflow Sohn, Matthias
2009-04-27 23:05 ` [PATCH JGIT] Method invokes inefficient new String(String) constructor Sohn, Matthias
2009-04-27 23:17 ` Shawn O. Pearce
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