RFR [9]: 8050142: Optimize java.util.Formatter (original) (raw)

Andrej Golovnin andrej.golovnin at gmail.com
Mon Jul 14 11:08:14 UTC 2014

Hi Claes,

in the method Formatter$FormatSpecifier#justify(String) you can pre-calculate the capacity of the StringBuilder to avoid array copying, e.g. instead of

2931 StringBuilder sb = new StringBuilder();

use this one:

2931 StringBuilder sb = new StringBuilder(s.length() + sp);

And in the method Formatter$FormatSpecifier#justify(StringBuilder) you can avoid creation of the StringBuilder object in the line 2956, e.g. instead of:

2956 StringBuilder tmp = new StringBuilder(sp); 2957 for (int i = 0; i < sp; i++) { 2958 tmp.append(' '); 2959 } 2960 sb.insert(0, tmp);

you can write this:

2956 char[] tmp = new char[sp]; 2957 Arrays.fill(tmp, ' '); 2958 sb.insert(0, tmp);

It's not a big improvement but maybe you can change the line

3781 exp.append("0").append(len - 1);

to use the character-based API to append a single character.

Best regards, Andrej Golovnin

On Mon, Jul 14, 2014 at 12:07 PM, Claes Redestad <claes.redestad at oracle.com> wrote:

Hi,

please review this patch which optimizes away some allocations from java.util.Formatter and achieve 1.1-1.3x speedups of micros targetting String.format. See bug for more details. webrev: http://cr.openjdk.java.net/~redestad/8050142/webrev.0 bug: https://bugs.openjdk.java.net/browse/JDK-8050142 Testing: JPRT, jtreg (java/lang/String, java/util/Formatter), SPECjbb2013 and microbenchmarks Thanks! /Claes

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