IsPrimeOld.java Source code

Introduction

Here is the source code for IsPrimeOld.java

Source

//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;
    }
}