Hope I will not get banned for too many posts :)
The code below does not want to compile. I get ""Possible Loss of Precision"
in the lines:
'j=last;'

'sito[j]=i;'

'increase(i,last);'

Whats wrong with it ?
////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////

package narzedzia;
public  class LiczbyPierwsze {
protected final static long length = 21;
protected final static long sito [] = new long [(long)1<<length];

// inicjalizacja sita :

{
sito[0]=1;
sito[1]=1;

long last  = 0L;
long j;
long i =2;
while(i<length){  // in i we got the following prime
 j=last;
 while(j<length){    // we mark the numbers whose smallest divisor is i
  if(sito[j]== j);
   sito[j]=i;
  j+=i;
  }
increase(i,last);  // we count the next prime for the sive
}
}

public final static long czyPierwsza(long x ){
;
return 0;
}

public final static long naCzynnikiPierwsze(long x){
;
return 0;
}
private final static void increase(long x, long last){
while(sito[last++]!=(long)0);
   x =(long)sito[last];
}

}