Java代码如何打印1000以内所有的质数呢?

质数简介

质数指
    大于1的自然数中
    除了1和它本身以外不再有其他因数的自然数
我们将这个数称之为质数

1000以内的质数列表

  
2	3	5	7	11	13	17	19	23	29	31	37
	41	43	47	53	59	61	67	71
73	79	83	89	97	101	103	107	109	113	127	131
	137	139	149	151	157	163	167	173	
179	181	191	193	197	199	211	223	227	229	233	239
	241	251	257	263	269	271	277	281	
283	293	307	311	313	317	331	337	347	349	353	359
	367	373	379	383	389	397	401	409	
419	421	431	433	439	443	449	457	461	463	467	479
	487	491	499	503	509	521	523	541	
547	557	563	569	571	577	587	593	599	601	607	613
	617	619	631	641	643	647	653	659	
661	673	677	683	691	701	709	719	727	733	739	743
	751	757	761	769	773	787	797	809	
811	821	823	827	829	839	853	857	859	863	877	881
	883	887	907	911	919	929	937	941	
947	953	967	971	977	983	991	997	

一共有168个

使用stream对1000以内的所有数进行判断,符合条件的作为质数返回

package com.java265.test;
 
import java.util.list;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;
 
public class PrintPrimeNumber {
 
    public static void main(String[] args) {
 
        long count = Stream.iterate(0, n -> n + 1)
                .limit(1000)
                .filter(TestPrime::isPrime)
                .peek(x -> System.out.format("%s\t", x))
                .count();
 
        System.out.println("\nTotal: " + count);
    }
 
    public static boolean isPrime(int number) {
 
        if (number <= 1) return false; // 1 is not prime and also not composite
        return !IntStream.rangeClosed(2, number / 2).anyMatch(i -> number % i == 0);
    }
}

使用BigInteger::nextProbablePrime

Stream.iterate(BigInteger.valueOf(2), BigInteger::nextProbablePrime)
			.limit(168)
			.forEach(x -> System.out.format("%s\t", x));
或使用Java 9的BigInteger.TWO

Stream.iterate(BigInteger.TWO, BigInteger::nextProbablePrime)
			.limit(168)
			.forEach(x -> System.out.format("%s\t", x));

package com.java265.test;
import java.util.ArrayList;
import java.util.List;
public class PrintPrimeNumber2 {
    public static void main(String[] args) {
        List<Integer> collect = new ArrayList<>();
        for (int i = 0; i < 1000; i++) {
            if (isPrime(i)) {
                collect.add(i);
            }
        }
 
        for (Integer prime : collect) {
            System.out.format("%s\t", prime);
        }
 
        System.out.println("\nTotal: " + collect.size());
 
    }
 
    private static boolean isPrime(int number) {
 
        if (number <= 1) return false;    //  1 is not prime and also not composite
 
        for (int i = 2; i * i <= number; i++) {
            if (number % i == 0) {
                return false;
            }
        }
        return true;
    }
}

快速收集质数

package com.java265.test;
import java.util.Arrays;
import java.util.BitSet;
import java.util.LinkedList;
import java.util.List;
public class PrintPrimeNumber3 {
    public static void main(String[] args) {
        List<Integer> result = primes_soe_array(1000);
 
        result.forEach(x -> System.out.format("%s\t", x));
 
        System.out.println("\nTotal: " + result.size());
 
    }
 
    /**
     * Sieve of Eratosthenes, true = prime number
     */
    private static List<Integer> primes_soe(int limit) {
 
        BitSet primes = new BitSet(limit);
        primes.set(0, false);                       
        primes.set(1, false);                       
        primes.set(2, limit, true);
 
        for (int p = 2; p * p <= limit; p++) {
            if (primes.get(p)) {
                for (int j = p * 2; j <= limit; j += p) {
                    primes.set(j, false);
                }
            }
        }
 
        List<Integer> result = new LinkedList<>();
        for (int i = 0; i <= limit; i++) {
            if (primes.get(i)) {
                result.add(i);
            }
        }
 
        return result;
 
    }
 
    // Some developers prefer array.
    public static List<Integer> primes_soe_array(int limit) {
 
        boolean primes[] = new boolean[limit + 1];
        Arrays.fill(primes, true);
        primes[0] = false;
        primes[1] = false;
 
        for (int p = 2; p * p <= limit; p++) {
            if (primes[p]) {
                for (int j = p * 2; j <= limit; j += p) {
                    primes[j] = false;
                }
            }
        }
 
        List<Integer> result = new LinkedList<>();
        for (int i = 0; i <= limit; i++) {
            if (primes[i]) {
                result.add(i);
            }
        }
        return result;
    }
}