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From: Jan Burse <janburse@fastmail.fm>
Newsgroups: comp.lang.java.programmer
Subject: Bulk Array Element Allocation, is it faster?
Date: Sun, 25 Sep 2011 03:17:19 +0200
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Dear All,

I just wonder wether modern JIT do optimize
Code of the following form:

     Bla[] bla = new Bla[n];
     for (int i=0; i<n; i++) {
         bla[i] = new Bla();
     }

When I use the above in my code, my application
spends 8800 ms in the benchmark I have.

When I then change the code to:

     Bla[] bla = new Bla[n];

     ...

     if (bla[i]==null)
        bla[i] = new Bla();

     ..

So instead of allocating all elements at once,
I will allocate them on demand in the subsequent
flow of my application.

When I use the above in my code, my application
now suddently sends 9600 ms in the benchmark
I have.

So I wonder whether eventually the JIT has
a way to detect the bulk allocate of the first
version and transform it into something more
efficient than my lazy allocation.

Any clues?

Bye