问编写算法所需的帮助

EN

Collection<Integer> generateNumbers(int n) {
    Collection<Integer> numbers = new HashSet<Integer>();
    Random rand = new Random();
    int max = 0;        
    int min = 0;
    for(int i=0;i<n;i++){
        max=(max*10)+n;
        min=(min*10)+1;
    }
    while(numbers.size()<n){
        int random = rand.nextInt(max-min+1)+min;
        int temp = random;
        boolean good = true;
        Set<Integer> digits = new HashSet<Integer>();
        while(temp>0 && good){
            int reminder = temp%10;
            if(reminder > 0 && reminder <= n ){ 
                digits.add(reminder);
            }else
                good = false;
            temp/=10;
        }       
        if(good && digits.size() == n)
        numbers.add(random);
    }       
    return numbers;
}