Hello,
It's me again, well, I've had a look too to the Java implementation
of the isByte method and I took care of your remarks to reimplement
it (thank you). So here are the results:
old method from Commons Validator :
public static boolean isByte(String value) {
return formatByte(value) != null;
}
public static Byte formatByte(String value) {
Byte result = null;
try {
result = new Byte(value);
} catch (Exception e) {
}
return result;
}
And the new one which do exactly what is needed, that's to
say return true or false and doesn't throw any exception:
public static final boolean isByte( String s )
{
// should never happen in JOE
if( s == null )
return false;
int result = 0;
boolean negative = false;
int i = 0;
int max = s.length();
int limit;
int multmin;
int digit;
if( max > 0 )
{
if( s.charAt( 0 ) == '-' )
{
negative = true;
limit = Integer.MIN_VALUE;
i++;
}
else
{
limit = -Integer.MAX_VALUE;
}
multmin = limit / 10; // radix
if( i < max )
{
digit = Character.digit( s.charAt( i++ ), 10 ); // radix
if( digit < 0 )
return false;
else
result = -digit;
}
while( i < max )
{
// Accumulating negatively avoids surprises near MAX_VALUE
digit = Character.digit(s.charAt(i++),10); // radix
if( digit < 0 )
return false;
if( result < multmin )
return false;
result *= 10; // radix
if( result < limit + digit )
return false;
result -= digit;
}
}
else
return false;
if( negative )
{
if( i > 1 )
return !(result < Byte.MIN_VALUE || result > Byte.MAX_VALUE );
else
return false; /* Only got "-" */
}
else
return !(-result < Byte.MIN_VALUE || -result > Byte.MAX_VALUE );
}
And the results for this test:
System.out.println((new java.util.Date()).getTime()+"");
for( int i = 0; i < 100000; i++ )
{
isByteApache( "300" );
isByteApache( "5" );
}
System.out.println((new java.util.Date()).getTime()+"");
for( int i = 0; i < 100000; i++ )
{
isByte( "300" );
isByte( "5" );
}
System.out.println((new java.util.Date()).getTime()+"");
if( isByteApache( "300" ) )
throw new IllegalStateException("problem");
if( !isByteApache( "5" ))
throw new IllegalStateException("problem");
if( isByte( "300" ) )
throw new IllegalStateException("problem");
if( !isByte( "5" ))
throw new IllegalStateException("problem");
if( isByte( "-300" ) )
throw new IllegalStateException("problem");
if( !isByte( "-5" ))
throw new IllegalStateException("problem");
2093ms for the first loop and... 90ms for the second one => 25 times
faster!
Thank you again :-)
Loïc
> ps: If you should read something about Knuth, read only his most famous
> quote. really.
Which is...? (the title please)
> With Joe, you're taking the optimization step by the wrong end IMHO
What do you mean by this? Tell me please :-)
Extranet
[EMAIL PROTECTED] - 07/11/2002 17:19
Veuillez répondre à [EMAIL PROTECTED]
Pour : ant-dev
cc :
Objet : Re: Réf. : RE: Réf. : Re: Commons Validator
----- Original Message -----
From: <[EMAIL PROTECTED]>
>Well it's just about 8% faster:
[...]
ah.
Byte.parseByte(String) is faster, you avoid an allocation.
Byte.parseByte(String, 10) is even faster you avoid a method call
int i = Integer.parseInt(s, radix);
return !(i < Byte.MIN_VALUE || i > MAX_VALUE)
is even more faster. you avoid a method call and and an exception
and yet I suggest to copy/paste the Integer.parseInt method and use your
own
by remove the exceptions to make it even more faster by removing yet
another
method call and exception.
>ps: don't have the time to make a patch (sorry)
I see. Time problem.
ps: If you should read something about Knuth, read only his most famous
quote. really.
With Joe, you're taking the optimization step by the wrong end IMHO
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