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Groups > comp.lang.java.programmer > #7569

Re: StringBuilder

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bob schrieb:
> Is there any way to use StringBuilder but with + signs instead of
> append?

The + in Java does already internally use StringBuilder.

There is only an issue when you want to accumulate a string
value. If you then explicitly use StringBuilder you are
faster, because you save the new StringBuilder() and toString().

So this is faster, since it uses 1 new and 1 toString():

     StringBuilder buf=new StringBuilder();
     for (int i=0; i<100; i++) {
        buf.append(i);
        buf("*");
        buf.append(i);
        buf.append("=");
        buf.append((i*i));
        buf.append("\n");
     }
     System.out.println(buf.toString());

Whereby this code is slower:

     String res="";
     for (int i=0; i<100; i++) {
        res+=i+"*"+i+"="+(i*i)+"\n";
     }
     System.out.println(res);

It is translated to the following code by the compiler, and
thus uses 100 new and 100 toString():

     String res="";
     for (int i=0; i<100; i++) {
         StringBuilder _buf=new StringBuilder(res);
         _buf.append(i);
         _buf("*");
         _buf.append(i);
         _buf.append("=");
         _buf.append((i*i));
         _buf.append("\n");
         res=_buf.toString();
     }
     System.out.println(res);

For more information see for example here:
http://caprazzi.net/posts/java-bytecode-string-concatenation-and-stringbuilder/

Best Regards

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Thread

StringBuilder bob <bob@coolgroups.com> - 2011-09-04 19:45 -0700
  Re: StringBuilder Arne Vajhøj <arne@vajhoej.dk> - 2011-09-04 22:53 -0400
  Re: StringBuilder Jan Burse <janburse@fastmail.fm> - 2011-09-05 05:27 +0200
    Re: StringBuilder Arne Vajhøj <arne@vajhoej.dk> - 2011-09-05 19:34 -0400
      Re: StringBuilder Wanja Gayk <brixomatic@yahoo.com> - 2011-09-11 16:35 +0200
        Re: StringBuilder Arne Vajhøj <arne@vajhoej.dk> - 2011-09-11 16:48 -0400
    Re: StringBuilder Roedy Green <see_website@mindprod.com.invalid> - 2011-09-05 17:01 -0700
  Re: StringBuilder Roedy Green <see_website@mindprod.com.invalid> - 2011-09-05 11:08 -0700
    Re: StringBuilder Jan Burse <janburse@fastmail.fm> - 2011-09-05 23:54 +0200
      Re: StringBuilder Jan Burse <janburse@fastmail.fm> - 2011-09-06 00:06 +0200
      Re: StringBuilder Roedy Green <see_website@mindprod.com.invalid> - 2011-09-05 17:03 -0700
        Re: StringBuilder Jan Burse <janburse@fastmail.fm> - 2011-09-06 08:53 +0200

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