initialize String

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Petterson Mikael - 21 Sep 2004 07:49 GMT

Hi,

Found in the code that I am maintaining:

private String currentOperation;
currentOperation = new String("deleteGroup()");

Is it not better to write:

private String currentOperation;
currentOperation = "deleteGroup()";

I am not sure of the difference.
Any ideas which to prefer.

//Mikael

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Aki \ - 21 Sep 2004 08:00 GMT

> Hi,
>
[quoted text clipped - 7 lines]
> private String currentOperation;
> currentOperation = "deleteGroup()";

No. Here you don't actually initialize the currentOperation String.
(Missing the "new String(...)" part).
You can't do

private String currentOperation = new String();
currentOperation = "deleteGroup()";

either, because Strings are static, so you can't modify a String after
you've initialized it.

If you want to modify the contents of currentOperation, you've got to
change it to a StringBuffer.

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Stefan Schulz - 21 Sep 2004 09:08 GMT

> Hi,
>
[quoted text clipped - 10 lines]
> I am not sure of the difference.
> Any ideas which to prefer.

Why not just use

private String currentOperation = "deleteGroup()";

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Aki \ - 21 Sep 2004 09:51 GMT

> Why not just use
>
> private String currentOperation = "deleteGroup()";

Isn't it supposed to be done like this:

private String currentOperation = new String("deleteGroup()");

?

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Stefan Schulz - 21 Sep 2004 10:02 GMT

On Tue, 21 Sep 2004 11:51:13 +0300, Aki "Sus" Laukkanen
<aki.laukkanenREMOVETHIS@helsinki.fi> wrote:

>> Why not just use
>> private String currentOperation = "deleteGroup()";
>
> Isn't it supposed to be done like this:
>
> private String currentOperation = new String("deleteGroup()");

Why? You can use a String literal in any place you can use a String
Object. After all, the Literal
is nothing but a fancy way of writing an Object. (you could also use
private String currentOperation = new String(new char[]{'d', 'e', 'l',
'e', 't', 'e', 'G', 'r', 'o', 'u', 'p',
'(', ')'}); if you really insist, but this has no advantage over using a
literal.

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Tor Iver Wilhelmsen - 21 Sep 2004 10:08 GMT

> private String currentOperation = new String("deleteGroup()");

No, that creates an unnecessary String object. String literals are
String objects on their own.

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Aki \ - 21 Sep 2004 10:15 GMT

>>private String currentOperation = new String("deleteGroup()");
>
> No, that creates an unnecessary String object. String literals are
> String objects on their own.

Ah.
Wasn't aware of that. My bad. :)

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-Aki "Sus" Laukkanen

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Tony Morris - 22 Sep 2004 07:43 GMT

> Hi,
>
[quoted text clipped - 7 lines]
> private String currentOperation;
> currentOperation = "deleteGroup()";

Yes, it is better - since you are making use of the "String literal pool"
(an abstract concept).
It will give a minor performance increase and more readable code.

I tend to get annoyed at verbose code that does nothing other than hinder
readability and give a performance hit (regardless of how negligible it
might be) simply due to misinformation of the language that the developer is
using. I do, however, have tolerance for those who are learning, making
mistakes and gaining a better understanding as a result (if this is the
case, notify the author of the code that you know something that might be in
their interest).

I suggest using the JLS as a reference, specifically the section on "String
literals" - I'd look it up, but I'm sure that you are more than capable.

Good luck.

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Thomas G. Marshall - 25 Sep 2004 14:50 GMT

Tony Morris coughed up:

>> Hi,
>>
[quoted text clipped - 13 lines]
>
> I tend to get annoyed at verbose code that does nothing [...]

I'd like to point out that the following:

(str1 comes from StringBuffer)
String str2 = new String(str1);

is *actually important*. There are times when the underlying array within
the String (it's actually in there, go look), can grow out of control even
though the string part is fairly small.

This was best described by Jon Skeet a long time ago:

http://groups.google.com/groups?selm=MPG.160abca06e214209989e47%40mrmog.peramon.com

<QUOTE from Jon Skeet, 13-Sep-2001>
Consider:

StringBuffer largeBuffer = new StringBuffer (100000);
largeBuffer.append ("small text");

String largeString = largeBuffer.toString();
map.put (largeString, value); // Whoops, 200K of memory gone

// This copies the contents rather than sharing the buffer,
// so we end up with a much smaller memory footprint
String smallString = new String (largeString);
map.put (smallString, value);

It's the only worthwhile use of the String constructor which takes a
String that I've seen. It's *very* useful when reading large numbers of
strings in from files using a BufferedReader, as the BufferedReader
starts off with an 80 character buffer each time. In the case of reading
a dictionary, you could be wasting vast amounts of memory in unfilled
buffers.
</QUOTE>

...[rip]...

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initialize String

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