Is Prime
//package util; import java.util.ArrayList; import java.util.List; public class IsPrimeOld { private static List<Long> primeList = new ArrayList<Long> () ; private static long maxNumber = 3 ; private static long newMaxNumber = 0 ; private boolean isPrimer; private long number; public IsPrimeOld ( long number ) { this .number = number; if ( number == 2L || number == 3L ) { this .isPrimer = true ; } else if ( number < maxNumber ) { this .isPrimer = initIsPrimer () ; } else { newMaxNumber = number; initPrimeList () ; this .isPrimer = initIsPrimer () ; } } private static void initPrimeList () { long start = System.currentTimeMillis () ; if ( maxNumber == 3 ) { primeList.add ( 2L ) ; primeList.add ( 3L ) ; } for ( long i = maxNumber; i < newMaxNumber; i += 2 ) { long j = 1 ; double temp = Math.sqrt ( i ) ; for ( j = 2 ; j < temp; j++ ) { if ( i % j == 0 ) break ; } if ( j == ( long ) temp + 1 ) { primeList.add ( i ) ; } } long end = System.currentTimeMillis () ; maxNumber = newMaxNumber; } private boolean initIsPrimer () { long start = System.currentTimeMillis () ; boolean b = true ; for ( Long primer : primeList ) { if ( number % primer == 0 ) { b = false ; break ; } } long end = System.currentTimeMillis () ; return b; } }
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