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Re: [cdt-dev] Of Char[] and String

Ah, memories ;)
This came at a time when we were very worried about size/performance of the parser. The JDT seemed to get away with things using char arrays instead of Strings. Essentially that removes the extra objects which is significant since the parser creates a lot of "strings". To keep things uniform, we used char arrays all over the place.
I don't get your statement about String being more efficient than char array. Since all String does is wrap char arrays with algorithms. I would do a little more research on whether Strings are actually smaller. Constants, maybe, since we may be generating code to convert them from compiler generated String. A good compiler would optimize that out.  At any rate we don't have that many constants, so we didn't worry about that much.
On Mon, Jul 20, 2009 at 2:43 PM, Alex Blewitt <alex.blewitt@xxxxxxxxx> wrote:
As a general observation, I'm confused with the amount of char[] that happens in the CDT codebase. Is this a general consequence of C programmers working in Java, or are there underlying reasons? I happen to come across this today:

    private static final char[] EMPTY_CHAR_ARRAY = new char[0];
    private static final char[] ONE = "1".toCharArray(); //$NON-NLS-1$

The problem with char[] is that it's generally a less efficient one for storage than the underlying String model is, and in any case, you end up with the String being backed by a similar array in the first place (which is then interned). 

Consider the following class:

public class Tes
  public static final char[] foo = "1".toCharArray();
  // public static final char[] foo = {'1'};
  // public static final String foo = "1";

If I compile this (Mac OS X with Java 6) I get the following sizes of class file generated:

char with toCharArray = 329b
char with in-line array = 272b
String = 248b

What I can't understand is why we have the string "1" (which will take up space in the Class' intern pool) and then taking up more space than if we'd just used the string on its own. 

There's probably a reason, but one that isn't immediately obvious to me. Perhaps someone could enlighten me? It's probably all related to the fact that Token has a char[] getCharImage(), but that in itself just lends the question to 'why doesn't that return a String ...'


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