Java编程把一个给出的整数写成四个素数之和

Java代码如下:

import java.util.ArrayList;
import java.util.List;

public class PrimeNumberSum {

    public static void main(String[] args) {
        int num = 100;
        List<Integer> primes = getPrimes(num);
        System.out.println("The prime numbers less than or equal to " + num + " are: " + primes);

        List<List<Integer>> results = findFourPrimesSum(num, primes);
        System.out.println("The sums of four prime numbers that equal to " + num + " are:");
        for (List<Integer> result : results) {
            System.out.println(result);
        }
    }

    // 获取小于等于n的所有素数
    public static List<Integer> getPrimes(int n) {
        List<Integer> primes = new ArrayList<>();
        boolean[] isPrime = new boolean[n+1];
        for (int i = 2; i <= n; i++) {
            isPrime[i] = true;
        }
        for (int i = 2; i <= n; i++) {
            if (isPrime[i]) {
                primes.add(i);
                for (int j = i*i; j <= n; j += i) {
                    isPrime[j] = false;
                }
            }
        }
        return primes;
    }

    // 找到所有由四个素数相加等于n的组合
    public static List<List<Integer>> findFourPrimesSum(int n, List<Integer> primes) {
        List<List<Integer>> results = new ArrayList<>();
        for (int i = 0; i < primes.size(); i++) {
            for (int j = i; j < primes.size(); j++) {
                for (int k = j; k < primes.size(); k++) {
                    for (int l = k; l < primes.size(); l++) {
                        if (primes.get(i) + primes.get(j) + primes.get(k) + primes.get(l) == n) {
                            List<Integer> result = new ArrayList<>();
                            result.add(primes.get(i));
                            result.add(primes.get(j));
                            result.add(primes.get(k));
                            result.add(primes.get(l));
                            results.add(result);
                        }
                    }
                }
            }
        }
        return results;
    }
}

该程序首先获取小于等于所给整数的所有素数，然后通过四重循环遍历素数列表，找到所有由四个素数相加等于所给整数的组合。最后将结果输出。