Java程序实现轮筛法生成指定范围内的素数

import java.io.*;

public class Main {
   // Maximum range
   static boolean numbers[] = new boolean[1000001];
   static void createMatrix() {
      // max range
      int range = 1000000;
      // Initially mark even numbers as non-prime and odd numbers as prime
      for (int p = 4; p <= range; ++p) {
         if (p % 2 == 0)
            numbers[p] = false;
         else
            numbers[p] = true;
      }
      // Traverse all odd numbers and update if the number is not prime
      for (int p = 3; p <= Math.sqrt(range); p += 2) {
         // If the number is prime
         if (numbers[p] == true) {
            // Update all multiples of p as non-prime
            for (int q = p * p; q <= range; q += p) {
               numbers[q] = false;
            }
         }
      }
   }
   static void getPrimes (int left, int right) {
      System.out.println("Prime numbers in the given range are:");
      for (int p = left; p <= right; ++p) {
         // Printing prime numbers in the range
         if (numbers[p] == true) {
            System.out.print(p + " ");
         }
      }
   }
   public static void main(String[] args) {
      int left = 10;
      int right = 50;
      createMatrix();
      // Get prime numbers in the given range
      getPrimes(left, right);
   }
}

import java.util.*;

public class Main {
   static boolean checkForPrime(int num) {
      boolean isNumPrime = true;
      // Wheel of prime numbers
      int[] primes = { 7, 11, 13, 17, 19, 23, 29, 31 };
      // Base Case
      if (num < 2) {
         isNumPrime = false;
      }
      if (num % 2 == 0 || num % 3 == 0 || num % 5 == 0) {
         isNumPrime = false;
      }
      // Check in the wheel P is the layer of the wheel
      for (int p = 0; p < Math.sqrt(num); p += 30) {
         // Check for the list of Sieve in primes[]
         for (int pm : primes) {
            // When the prime number exceeds the square root of the num
            if (pm > Math.sqrt(num)) {
               break;
            }
            // If num is multiple of pm in the current wheel
            else {
               if (num % (pm + p) == 0) {
                  isNumPrime = false;
                  break;
               }
            }
            // When a number is non-prime in the current layer
            if (!isNumPrime)
               break;
         }
      }
      return isNumPrime;
   }
   public static void main(String args[]) {
      int left = 10;
      int right = 50;
      System.out.println("Prime numbers in the given range are :");
      for (int p = left; p <= right; ++p) {
         if (checkForPrime(p) == true) {
            System.out.print(p + " ");
         }
      }
   }
}