[Java] Eratosthenes sieve method for verifying prime numbers

The Eratosthenes sieve method, called the sieve or the AI sieve, is a simple algorithm for the prime number of the Eratosthenes proposed by the Greek mathematician. To get the full number of prime numbers within the natural n, the multiples of all primes of the root n must be removed, and the remainder is prime.

In order to get the total number of prime numbers within N, it is necessary to remove the multiples of all primes, and the remainder is prime. Give the range N of the value to be sifted to find the prime number within. First use 2 to sift, that is, 2 left, the number of 2 is removed, and then the next prime number, that is, 3 sieve, 3 left, the multiples of 3 is removed, then the next prime number 5 sieve, 5 left, the multiples of 5 are removed;

Java source code:

Package Test1.number;public class Eratosthenes {public static void main (string[] args) {int max = $; try {max = INTEGER.P Arseint (Args[0]);} catch (Exception e) {} boolean[] IsPrime = new Boolean[max + 1];for (int i = 0; I <= max; i++) isprime[i] = True;isprime [0] = isprime[1] = false;int n = (int) Math.ceil (MATH.SQRT (max)); for (int i = 0; I <= N, i++) {if (Isprime[i]) for (int j = 2 * i; j <= Max; j = j + i) isprime[j] = false;} int Largest;for (largest = max;!isprime[largest]; largest--); System.out.println ("the largest prime less than or equal to" + max+ "is" + largest);}}

Operation Result:

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[Java] Eratosthenes sieve method for verifying prime numbers