[JGIT PATCH 09/13] Replace inefficient new String(String) constructor to silence FindBugs

From: Shawn O. Pearce <spearce@spearce.org>
Date: Apr 28, 2009, 21:12 UTC
Message-ID: <1240953146-12878-10-git-send-email-spearce@spearce.org>
In-Reply-To: <1240953146-12878-9-git-send-email-spearce@spearce.org>

FindBugs keeps reporting that our usage of new String(String) is not the most efficient way to construct a string.

http://thread.gmane.org/gmane.comp.version-control.git/113739/focus=113787

Show 11 quoted lines

> 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.

Another way to force this new unique String instance with its own private char[] is to use a StringBuilder and append onto it the ref name. This shouldn't be a warning for FindBugs, but it would accomplish the same goal of producing 1 clean copy, with no extra transient temporary array.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
CC: Yann Simon <yann.simon.fr@gmail.com>
CC: Matthias Sohn <matthias.sohn@sap.com>
---
 .../src/org/spearce/jgit/lib/RefDatabase.java      |    3 ++-
 1 files changed, 2 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..bccf2d0 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 +447,8 @@ 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 = new StringBuilder(p.length() - (sp + 1))
+							.append(p, sp + 1, p.length()).toString();
 					last = new Ref(Ref.Storage.PACKED, name, name, id);
 					newPackedRefs.put(last.getName(), last);
 				}

-- 
1.6.3.rc1.205.g37f8