我正在尝试以 Python 为基础学习 Java,所以请多多包涵。
我正在实现一种 Eratosthenes 筛法(我在 Python 中有一个;试图将其转换为 Java):
def prevPrimes(n):
"""Generates a list of primes up to 'n'"""
primes_dict = {i : True for i in range(3, n + 1, 2)}
for i in primes_dict:
if primes_dict[i]:
num = i
while (num * i <= n):
primes_dict[num*i] = False
num += 2
primes_dict[2] = True
return [num for num in primes_dict if primes_dict[num]]
这是我将其转换为 Java 的尝试:
import java.util.*;
public class Sieve {
public static void sieve(int n){
System.out.println(n);
Map primes = new HashMap();
for(int x = 0; x < n+1; x++){
primes.put(x, true);
}
Set primeKeys = primes.keySet();
int[] keys = toArray(primeKeys); // attempt to convert the set to an array
System.out.println(primesKeys); // the conversion does not work
for(int x: keys){
System.out.println(x);
}
// still have more to add
System.out.println(primes);
}
}
我得到的错误是它找不到方法toArray(java.util.Set)
。我怎样才能解决这个问题?