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Hi,
For the following to snips, which one do you think is more efficient?

snip1:
BufferedWriter bw = new BufferedWriter(new
OutputStreamWriter(System.out));
bw.write("abc" + "def");

snip2:
BufferedWriter bw = new BufferedWriter(new
OutputStreamWriter(System.out));
bw.write("abc");
bw.write("def");


--
Best regards,
Qingjia Zhu
Q@z@J

metfan wrote:
> Hi,
> For the following to snips, which one do you think is more efficient?
>
> snip1:
> BufferedWriter bw = new BufferedWriter(new
> OutputStreamWriter(System.out));
> bw.write("abc" + "def");

I think the compiler probably compiles this to bw.write("abcdef"), which
would be faster, but in general if you had bw.write(a+b) with a and b
String variable, then there would actually be a StringBuffer
instanstiated just for joining a and b. So that would definitely be
slower than just writing a and then b to the Buffer.

> snip2:
> BufferedWriter bw = new BufferedWriter(new
> OutputStreamWriter(System.out));
> bw.write("abc");
> bw.write("def");



--


Let's not weep for their evil deeds,
but for their lack of imagination
(Nick Cave)

metfan <qjzhupublic@___NoSpam__yahoo.ie> wrote:
> For the following to snips, which one do you think is more efficient?
>
> snip1:
> BufferedWriter bw = new BufferedWriter(new
> OutputStreamWriter(System.out));
> bw.write("abc" + "def");
>
> snip2:
> BufferedWriter bw = new BufferedWriter(new
> OutputStreamWriter(System.out));
> bw.write("abc");
> bw.write("def");

The first, as it compiles to the same as:

BufferedWriter bw = new BufferedWriter(new
OutputStreamWriter(System.out));
bw.write("abcdef");

because literal strings are concatenated at compile time.

--
Jon Skeet - <>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

>> For the following to snips, which one do you think is more efficient?
>>
>> snip1:
>> BufferedWriter bw = new BufferedWriter(new
>> OutputStreamWriter(System.out));
>> bw.write("abc" + "def");
>>
>> snip2:
>> BufferedWriter bw = new BufferedWriter(new
>> OutputStreamWriter(System.out));
>> bw.write("abc");
>> bw.write("def");
>
> The first, as it compiles to the same as:
>
> BufferedWriter bw = new BufferedWriter(new
> OutputStreamWriter(System.out));
> bw.write("abcdef");
>
> because literal strings are concatenated at compile time.
>

Well.. what if:

snip1:
BufferedWriter bw = new BufferedWriter(new
OutputStreamWriter(System.out));
String a = new String("abc");
String b = new String("def");
bw.write(a + b);

snip2:
BufferedWriter bw = new BufferedWriter(new
OutputStreamWriter(System.out));
String a = new String("abc");
String b = new String("def");
bw.write(a);
bw.write(b);


--
Best regards,
Qingjia Zhu
Q@z@J

"metfan" <qjzhupublic@___NoSpam__yahoo.ie> wrote in message
news...
> Well.. what if:
>
> snip1:
> BufferedWriter bw = new BufferedWriter(new
> OutputStreamWriter(System.out));
> String a = new String("abc");
> String b = new String("def");
> bw.write(a + b);
>
> snip2:
> BufferedWriter bw = new BufferedWriter(new
> OutputStreamWriter(System.out));
> String a = new String("abc");
> String b = new String("def");
> bw.write(a);
> bw.write(b);

You won't notice any real difference, but #1 would be faster, since String
concatentation is a lot faster thn an extra I/O call.

>
> --
> Best regards,
> Qingjia Zhu
> Q@z@J

metfan wrote:
> Well.. what if:
>
> snip1:
> BufferedWriter bw = new BufferedWriter(new
> OutputStreamWriter(System.out));
> String a = new String("abc");
> String b = new String("def");
> bw.write(a + b);
>
> snip2:
> BufferedWriter bw = new BufferedWriter(new
> OutputStreamWriter(System.out));
> String a = new String("abc");
> String b = new String("def");
> bw.write(a);
> bw.write(b);

In that case, the second one is faster, for the reason Bjoern gave. But
you probably shouldn't worry.

In article <MPG.1a02e94f7f5c63fc9896c1@10.1.1.14>, Jon Skeet wrote:
> metfan <qjzhupublic@___NoSpam__yahoo.ie> wrote:
>> For the following to snips, which one do you think is more efficient?
>>
>> snip1:
>> BufferedWriter bw = new BufferedWriter(new
>> OutputStreamWriter(System.out));
>> bw.write("abc" + "def");
>>
>> snip2:
>> BufferedWriter bw = new BufferedWriter(new
>> OutputStreamWriter(System.out));
>> bw.write("abc");
>> bw.write("def");
>
> The first, as it compiles to the same as:
>
> BufferedWriter bw = new BufferedWriter(new
> OutputStreamWriter(System.out));
> bw.write("abcdef");
>
> because literal strings are concatenated at compile time.
Essentially, just compile the 2 codes snippets, and
use jad to decompile it. You would see what happens..

Simon Righarts wrote:

> You won't notice any real difference, but #1 would be faster, since String
> concatentation is a lot faster thn an extra I/O call.

There is no extra IO call because it's a BufferedWriter.

On Fri, 24 Oct 2003 16:21:25 +0800, metfan
<qjzhupublic@___NoSpam__yahoo.ie> wrote or quoted :

>String a = new String("abc");
> String b = new String("def");

that is just stuttering that creates new String objects to no purpose.

The net effect is the same as

String a = "abc";
String b = "def";

see http://mindprod.com/jgloss/newbie.html

A smart compiler could do the concatenation at compile time, though it
would not be guaranteed the way "abc" + "def" is.

--
Canadian Mind Products, Roedy Green.
Coaching, problem solving, economical contract programming.
See http://mindprod.com/jgloss/jgloss.html for The Java Glossary.

On Fri, 24 Oct 2003 22:14:05 +1300, "Simon Righarts"
<> wrote or quoted :

>You won't notice any real difference, but #1 would be faster, since String
>concatentation is a lot faster thn an extra I/O call.

Not necessarily. The string i/o could be just an arraycopy with a
buffered file. The concatenation allocates a String buffer, copies the
two strings, and then converts the StringBuffer into a String.

--
Canadian Mind Products, Roedy Green.
Coaching, problem solving, economical contract programming.
See http://mindprod.com/jgloss/jgloss.html for The Java Glossary.