Re: [PATCH JGIT] Method invokes inefficient new String(String) constructor
From: Yann Simon <hidden>
Date: 2016-06-15 22:46:25
2009/3/19 Shawn O. Pearce [off-list ref]:
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.
Thany you for the explanation. I learn something, and my tests confirm it. The p.substring(...) can keep the entire array of char by only updating the intern offset value. new String(p.subtring(...)) make sure that the variable contains only the final chars. Yann