Subj : Re: Performance: Another test of Java vs JavaScript ...
To   : Neil Kolban <kolban@kolban.com>
From : Igor Bukanov <igor@fastmail.fm>
Date : Fri Oct 17 2003 07:52 pm

If you replace the tests by:

public class Perf2 {
     public static void main(String[] args) {
     String string = "ABCDEFGHIJ";
     int i = 1;
     long start = System.currentTimeMillis();
	int length = 0;
     while (i<200000)
     {
         length += String.valueOf(i).length();
         i = i + 1;
     }
     long diff = System.currentTimeMillis() - start;
     System.out.println("Elapsed: " + diff+" length="+length);
     }
}

and

function myFunc()
{
     var time = (new Date()).getTime();
     var string = "ABCDEFGHIJ";
     var sub;
     var i;
     i = 1;
     var length = 0;
     while (i < 200000)
     {
         length += String(i).length;
         i = i + 1;
     }
     time = (new Date()).getTime() - time;

     print("time: "+time+"ms length="+length);

}

myFunc();


then on my Linux box and jdk 1.4.2 I got for Java 145ms and for JS 
1434ms while for the original case it was 42 versus 1227.  It seems Java 
compiler/JVM was smart enough to optimize away the constant expression 
as Sterling pointed above.


Neil Kolban wrote:
> Folks,
>  
> Here are a couple of code fragments.... the first is Java and the 2nd is 
> JavaScript running under Rhino.
>  
> ------------------------------------------------------------------------
> * *
> 
> *public* *class* Perf2 {
>     *public* *static* *void* main(String[] args) {
>     String string = "ABCDEFGHIJ";
>     String sub;
>     *int* i = 1;
>     *long* start = System.currentTimeMillis();
> *    while* (i<200000)
>     {
>         sub = string.substring(3,6);
>         i = i + 1;
>     }
> *    long* diff = System.currentTimeMillis() - start;
>     System.out.println("Elapsed: " + diff);
>     }   
> }
> 
> ------------------------------------------------------------------------
> 
> * *
> 
> *function* myFunc()
> {
> *    var* string = "ABCDEFGHIJ";
> *    var* sub;
> *    var* i;
>     i = 1;
> *    while* (i < 200000)
>     {
>         sub = string.substring(3, 6);
>         i = i + 1;
>     }
> }
> 
> myFunc();
> 
> ------------------------------------------------------------------------
> 
> The Java program takes 15 milliseconds, the JavaScript takes 850 
> milliseconds.  I understand compiled Java will probably be faster but I 
> am surprised at how much faster.
>

.