如何将ArrayList转换为数组，然后用Java返回它？

Question

我试图创建一个方法，创建一个给定数字的素因子列表，然后以数组的形式返回它们。除了将ArrayList转换为数组之外，其他一切似乎都很正常。此外，我不确定是否正确返回了数组

这是我的密码

static int[] listOfPrimes(int num) {
    ArrayList primeList = new ArrayList();
    int count = 2;
    int factNum = 0;

    // Lists all primes factors.
    while(count*count<num) {
        if(num%count==0) {
            num /= count;
            primeList.add(count);
            factNum++;
        } else {
            if(count==2) count++;
            else count += 2;
    }
}
int[] primeArray = new int[primeList.size()];
primeList.toArray(primeArray);
return primeArray;

当我编译

D:\JAVA>javac DivisorNumber.java
DivisorNumber.java:29: error: no suitable method found for toArray(int[])
            primeList.toArray(primeArray);
                     ^
method ArrayList.toArray(Object[]) is not applicable
  (actual argument int[] cannot be converted to Object[] by method invocatio
n conversion)
method ArrayList.toArray() is not applicable
  (actual and formal argument lists differ in length)
Note: DivisorNumber.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
1 error

此外，我不确定如何接收返回的数组，所以我也需要一些帮助。谢谢

Answer 1

将int[]数组更改为整数[]

static Integer[] listOfPrimes(int num) {
    List<Integer> primeList = new ArrayList<Integer>();
    int count = 2;
    int factNum = 0;

    // Lists all primes factors.
    while (count * count < num) {
        if (num % count == 0) {
            num /= count;
            primeList.add(count);
            factNum++;
        } else {
            if (count == 2)
                count++;
            else
                count += 2;
        }
    }

    return primeList.toArray(new Integer[0]);
}

Answer 2

int[] primeArray = primeList.toArray(new int[primeList.size()]);

但是我对用int比用Integer更能做到这一点没有信心