问对于没有数组的java编程，我可以使用哪些代码来实现最小、最大和平均？

EN

    import java.util.Scanner;
    public class TestScoreStatistics {

public static void main(String[] args) 
{
    double score;
    double max;
    double min;
    double average;
    Scanner keyboard = new Scanner(System.in);
    System.out.println("Please enter in test scores: ");
    score = keyboard.nextDouble();
    while(score >= 0 || score <= 100) {
        if(score >= 101 || score <= 0.9)
            System.out.println("The score must be between 0 - 100");
        else
            System.out.println("Please enter in test scores or type 999 to calculate final scores: ");
            score = keyboard.nextDouble();



        if(score == 999)
            System.out.println("The maximum score is - " + max + ".");
            System.out.println("The minimum score is - " + min + ".");
            System.out.println("The average score is - " + average + ".");          
    }   
}